Non-metallic Mineral Deposits
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Transcript of Non-metallic Mineral Deposits
Nonmetallic Mineral Deposits (GE3115)
Prof. Dr. H.Z. Harraz Presentation - Nonmetallic Deposits
A short series of lectures prepared for the
Third year of Special Geology, Tanta University
(GE3115)
2014- 2015
by
Hassan Z. Harraz
To Final Product
From raw material
Outline of Topic :
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 3
We will explore all of the above in Topic.
Earth Resources Reserves and resources Nonrenewable Mineral Resources What are industrial minerals? Why are industrial minerals so important? Geology of Industrial Minerals Deposits Classification of industrial minerals General characteristics of Non-metallic Deposits Factors important in evaluating an industrial minerals deposit Selected industrial rocks and minerals
1) ABRASIVES MINERALS
2) OLIVINE
3) CLAY MINERALS
4) FLUORITE
5) PERLITE
6) BUILDING STONES and Rip-rap
7) SULFUR ORE DEPOSITS
8) CALCIUM CARBONATE DEPOSITS
9) CHERT DEPOSITS
10) PHOSPHATE ORE DEPOSITS
11) EVAPORITE DEPOSITS
12) GYPSUM
13) SELECTED SOME NON-METALLIC METAMORPHIC DEPOSITS
13.1) Asbestos Deposits
13.2) Graphite Deposits
13.3) Talc, Soapstone, and Pyrophyllite
13.4) Selected Some Ornamental Metamorphic Stones
13.4.1) Marble 13.4.2) Quartzite 13.4.3) Serpentinite
What is a mineral?
Mineral: inorganic compound that occurs naturally in the earth’s crust
Solid
Regular internal crystalline structure
Definite chemical composition.
Rock is solid combination of one or more minerals.
What are orebody?
are aggregates of different minerals
have high concentrations of metal bearing minerals and
are hosted in barren “country” rock {Mined country rock is referred to as gangue (or
waste)}.
What is an Ore Deposit?
Ore deposit is an occurrence of minerals or metals in sufficiently high concentration to
be profitable to mine and process using current technology and under current economic conditions.
Ore deposits may be considered as:
Commercial mineral deposits (i.e., Ore: suitable for mining in the present
times) or
Non-commercial ore deposits (i.e., Protore: problems in mining, transportation,
prices....etc).
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Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 4
What is an Ore? Ore: Rock materials that exist in quantities that can be extracted and profitably mined
for a mineral (often a metal) or for minerals (metals).
An ore is a mass of mineralization within the Earth's surface which can be mined:
at a particular place;
at a particular time;
at a profit
Marketed for a profit.
Ore: refers to useful metallic minerals that can be mined at a profit and, in
common usage, to some non-metallic minerals such as fluorite and sulfur.
To be considered of value, an element must be concentrated above the level of
its average crustal abundance:
High Grade Ore; has high concentration of the mineral
Low Grade Ore: smaller concentration
Most non-metallic minerals are generally not called ores, but
rather they are called Industrial Minerals
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Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 5
What is gangue (or waste)? Gangue (or Waste): Minerals other than ore present in a rock.
Gangue (or Waste) is mineralized rock that is removed from a mine to provide
access to an underlying or nearby orebody containing at least one mineral of
value.
Types of Gangue (or Waste):
Typically pure barren materials;
Gangue material contained within the ore
Gangue (or Waste) rock can become ore at some later point in time.
Non-Metallic / commodity prices can change
Other values are discovered within the waste
New technology is developed
Cost of environmental protection becomes too high
Non-metallic minerals has been exhausted; too costly to close the mine.
Political factors
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Finding a Deposit
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The old fashioned way
of finding a mine was
your prospector with a
pick and shovel, a gold
pan, and a lot of luck.
Today, technologies used
include, but are not limited to,
exploration geology, geophysics, geochemistry, and satellite imagery.
Finding a Deposit
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 8
Geophysics
Geophysical exploration involves searching for favorable mineral deposits using the physical properties of rocks.
Geophysical investigations ground-penetrating radar studies or the use of seismic waves to show contrasting rock types.
The selected rock units of interest might then be mapped and sampled.
Geochemistry
Geochemists can determine the composition of what
lies below the Earth's surface by sampling soil. Soil at
the surface can carry a chemical signature of what lies
below, because of the movement of chemicals through
the rise and fall of the water table.
Positive geochemical results from surface sampling are
followed by a drilling program. Because of the great
expense, drilling is only carried out when the area is very
likely to contain substantial mineral deposits.
Drilling produces either rock fragments, or 'cores' of rock
for sampling to determine whether the mineral deposit
contains worthwhile concentrations of ore mineral
Geology
Geology is the study of the planet
Earth—the materials of which our planet
is made, the processes that act on these
materials, and the products formed.
Geologists use ground-mapping
techniques to identify features seen on
satellite images and aerial maps of large
tracts of the continent.
Remote sensing: Landsat and Satellite
Imagery
Ground-based surveys are expensive,
and one can often experience difficulty
in mapping large-scale structures.
However, large geological structures are
often readily visible on satellite imagery.
Reserves vs. Resources Reserves
Natural resources that
have been discovered &
can be exploited profitably
with existing technology.
Resources
The term ―resource‖ refers to the
total amounts of a commodity of
particular economic use that is
present in an area. These
estimates include both extractable
and non-extractable amounts of
this commodity.
Deposits that we know or believe to
exist, but that are not exploitable
today because of technological,
economical, or political reasons
Earth Resources may be
Renewable and/or Non-renewable
resources
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 9
Compared between Renewable and Non-renewable Mineral Resources
Renewable resources Non-renewable resources
Resource can be replenished over
relatively short time spans
Significant deposits take
millions of years to form; from
a human perspective there
are fixed quantities
Renewable can be:- It’s a one-time only deal. i) Perpetual Renewable
Resources
ii) Potentially Exhaustible/
Renewable Resources Once exploited and used the
resource is gone forever. Direct solar energy.
Energy from flowing water, sun, wind
Indirect effects related to
hydrological cycle (e.g., wind,
oceans, tides, running water
…etc).
Alternate/futuristic energy
resources:
Geothermal energy
Solar energy
• Fresh Air
• Fresh Water
• Fertile Soil
• Biodiversity: Examples include : Plants
Animals for food
Trees for lumber
Examples:
Fuels (coal, oil, natural
gas)
Metals (iron, copper,
uranium, gold)
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 10
Mineral Resources Non-metallic mineral deposits (NM)
Industrial Minerals (IM)): Sulfur, Gypsum, Coal, Barite, Salt, Clay, Feldspar, Borax, Lime, Magnesite, Potash, Phosphates, Silica, Fluorite, Asbestos, Abrasives, Mica.
Precious stones: Gem Minerals,
Construction minerals : Stone, Sand, Gravel, Limestone
Metallic mineral deposits or (Ore mineral deposits):
Ferrous metals: Iron and Steel, Cobalt, Nickel
Non-ferrous (or base metals): Copper, Zinc, Tin, Lead, Aluminum,
Titanium, Manganese, Magnesium, Mercury, Vanadium, Molybdenum,
Tungsten.
Precious metals: Silver, Gold, Platinum
Energy Resources(or Energy minerals):
Fossil Fuels: Coal, Oil, Natural Gas
Radioactive Minerals: Uranium
Geothermal Energy
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 11
Non-metals
Metals
Year
0
4
8
12
Billi
on
Can
$
16
1985
1990
1995
2000
Industrial Minerals and Metal Production
in Canada
50%
75%
(Industrial Minerals and
Structural Materials) ★
B.C.
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 13
Fig.2: Selected raw materials consumed in the U.S., 1900-95. For this graph, construction materials (crushed stone, sand and gravel) have been separated from the remainder of the industrial minerals to illustrate the upsurge in construction following the end of World War II
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Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 14 http://eps.berkeley.edu/courses/eps50/documents/lecture31.mineralresources.pdf
14
Coal, gas, oil, uranium
Iron ore, niobium, tantalum
Gold, Silver,
platinum
Diamond, gems
Brick, building stone, cement, clay, crushed
rock aggregate, gypsum, sand,
slate, gravel
Bentonite, industrial
carbonates, kaolin, magnesia, potash, salt, sand,
silica, sulphur
Bauxite/aluminium, cobalt, copper, lead, zinc, nickel,
molybdenum
Jewellery, monetary, industrial
Construction Jewellery, industrial
Ceramics, chemical, foundry casting, fillers/pigments,
fuel, gas, iron, steel, metallurgy, water
treatment
Construction, electrical/electronic
, engineering, manufacturing
Aerospace, contruction, electronic,
engineering, manufacturing, steel making
Electricity, organic chemical/plastics,
process fuel, transportation
Energy minerals Non-metallic minerals Metallic minerals
Minerals
Precious metals
Ferrous metals
Base metals
Construction minerals
Industrial minerals
Precious stones
End Use
Mineral Resources
Non-metallic Resources • Non-metallic resources - not mined to
extract a metal or an energy source. Construction Materials
• sand, gravel, limestone, and gypsum
Agriculture
• phosphate, nitrate and potassium
compounds.
Industrial uses
• rock salt, sulfur
Gemstones
• diamonds, rubies, etc.
Household and Business Products
• glass sand, diatomite
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Non-metallic Mineral Resources
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Typical examples of natural Industrial Mineral Deposits : Clays
Silica sand
Talc
Limestone/chalk
Gypsum
Pumice
Potash
Carbonate Minerals
Evaporite Salts
Phosphate
Sulphur
made from: Mullite bauxite, kaolin
Aluminas bauxite
Silicon carbide quartz + coke
ppt calcium
carbonate lime & CO2
Spinel magnesite + alumina
Soda salt + limestone + coal +
ammonia
Fused minerals alumina, magnesia, spinel
Typical examples of synthetic IM:
What are Non-metallic Deposits?
Steps in Obtaining Mineral Commodities 1) Prospecting: finding places where non-metallic minerals occur.
2) Mine exploration and development: learn whether non-metallic
minerals can be extracted economically.
3) Mining: extract non-metallic minerals from ground.
4) Beneficiation: separate non-metallic minerals from other mined
rock. (Mill)
5) Refining: extract pure mineral commodity from the ore mineral
(get the good stuff out of waste rock) (Refinery)
6) Transportation: carry commodity to market.
7) Marketing and Sales: Find buyers and sell the commodity.
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Geology of Industrial Minerals Deposits
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Geology provides the framework in which mineral exploration and the integrated procedures of remote sensing, geophysics, and geochemistry are planned and interpreted.
Non-metallic mineral deposits life cycle
Supply Sector
exploration
mineral finance
plant engineering
mining
processing
Logistics Sector
trading
port handling
mineral inspection
freight
warehousing/distribution
Consuming Market
Sector
direct market mineral consumer
intermediate market mineral consumer
end market mineral consumer
SUPPLY
DEMAND
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 22
Mine to market supply chain
Supply sector
Logistics sector
Consuming market sector
• centres of high population
• their economy - the driver
• directly influence demand for NM
Why are Non-Metallic Deposits so important?
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Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 23 23
Nonmetallic Deposits in your kitchen
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Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 24
IM in
your
kitchen
Glass/glasses/ light bulbs silica sand, limestone, soda ash, borates,
feldspar, lithium
Ceramic tiles/mugs/ plates
….etc.
kaolin, feldspar, talc, wollastonite, borates,
alumina, zirconia
Paint TiO2, kaolin, mica, talc, wollastonite, GCC, silica
Plastic white goods
eg. fridge, washer
talc, GCC, kaolin, mica, wollastonite, flame
retardants (ATH, Mg(OH)2)
Wooden flooring treatment materials- borates, chromite
Drinking water treatment materials- lime, zeolites
Wine/beer diatomite, perlite filters
Salt salt
Sugar lime in processing
Detergents/soap borates, soda ash, phosphates
Surfaces marble, granite
Books kaolin, talc, GCC, lime, TiO2 in paper
Oven glass petalite, borates
Heating elements fused magnesia insulators
Wallboard/plaster gypsum, flame retardants
Metal pots/cutlery mineral fluxes & refractories in smelting
Why are NM so important?
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Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 25
Main consuming market mineral sectors
Abrasives Foundry
Absorbents Glass
Agricultural Metallurgy
Cement Paint
Ceramics Pigments
Chemicals Paper
Construction Plastics
Oil well drilling Refractories
Electronics Flame retardants
Filtration Welding
General characteristics of Non-metallic Deposits
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 26
Highest volume and tonnage
low value, but vital commodities
High total value
Prices are more stable
NM are prerequisite raw materials for a wide range of industrial and domestic products
Recycling is not much of an issue
Price of the unit value is so low that transportation becomes a major issue
Rarely exported.
Feasibility study: Often need to find a market before looking for a nearby deposit
Depending on their uses, product purity and grain size may become very important factors in deciding the suitability and price of the commodity
NM support and add value to industrial sectors
Market demand drives NM supply
Classification of Non-metallic Deposits
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 27
End-use and genesis (Bates, 1960)
By unit price and bulk (Burnett, 1962)
Unit value, place value, representative value (Fisher,
1969)
Chemical and physical properties (Kline, 1970)
Geologic occurrence and end-use (Dunn, 1973)
Geology of origin (Harben and Bates, 1984)
Alphabetical (Harben and Bates, 1990; Carr, 1994)
Classification of Non-metallic deposits (Cont.) Rock classification Mineral classification
A) Igneous Rocks
Granite
Basalt and diabase
Pumice and pumicite
Perlite
B) Metamorphic Rocks
Slate
Marble
Serpentinite
Schist
Gneiss
C) Sedimentary Rocks
Sand and gravel
Sandstone
Clay
Limestone and dolomite
Phosphate rock
Gypsum
Salt
A) Igneous Minerals
Nepheline syenite
Feldspar
Mica
Lithium minerals
Beryl
B) Vein and Replacement Minerals
Quartz crystal
Fluorspar
Barite
Magnesite
C) Metamorphic Minerals
Graphite
Asbestos
Talc
Vermiculite
Emerald
D) Sedimentary Minerals and sulfur
Diatomite
Potash minerals
Sodium minerals
Borate
Nitrates
Sulfur
Factors important in evaluating a Non-metallic deposits
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 29
Customer specifications
Distance to customer (transportation)
Ore grade--concentration of the commodity in the deposit
By-products
Commodity prices
Mineralogical form
Grain size and shape
Undesirable substances
Size and shape of deposit
Ore character
Cost of capital
Location
Environmental consequences/ reclamation/bonding
Land status
Taxation
Political factors
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 30
1) Abrasives Minerals:
Abrasive mineral is a material, often a mineral, that is used to shape or finish a work-piece through rubbing which leads to part of the work-piece being worn away
Abrasives may be classified as either natural or synthetic.:
Selected Nonmetallic Deposits:
Naturally Abrasives Synthetic Abrasives
Coarse Abrasives Scrubbing Powders Soft Abrasives
Emery (impure corundum) Diatomite Ground Feldspar Silicon carbide
(carborundum)
Pumice Chalk Tungsten Carbide
Corundum Kaolin Boron carbide
Sandstone Ceramic iron oxide
Sand Corundum
Tripoli
Rouge
Garnet
Feldspar Steel abrasive
Calcite Zirconia alumina
Slags Quartz
Diamonds
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 31
The mineral olivine (when of gem quality, it is also called peridote) is a magnesium iron silicate with the formula (Mg+2, Fe+2)2SiO4.
Extracted from large dunite bodies.
Uses:
Slag conditioner in iron and steel making; refractory bricks.
Blast cleaning agent: Olivine is also used to tap blast furnaces in the steel industry, acting as a plug, removed in each steel run.
Foundry sand: The aluminium foundry industry uses olivine sand to cast objects in aluminium.
2) Olivine:
Clay Grades are categorized into six groups: 1) Kaolin or China clay: white, claylike material composed mainly of
kaolinite industrial applications: paper coating and filling, refractories, fiberglass and insulation, rubber, paint, ceramics, and chemicals
2) Ball clay: kaolin with small amount of impurities industrial application: dinnerware, floor tile, pottery, sanitary ware.
3) Fire clays: kaolin with substantial impurities (diaspore, flint) industrial applications: refractories
4) Bentonite (smectite): clay composed of smectite minerals, usually montmorillonite industrial applications: Oil well drilling fluids,
suspending agents; drilling muds, foundry sands 5) Fuller’s earth: nonplastic clay high in magnesia, a similar to bentonite
industrial applications: absorbents 6) Shale: laminated sedimentary rock consisting mainly of clay minerals
mud industrial application: raw material in cement and brick manufacturing
3) Clay minerals:
4) Fluorite (or Fluorspar): Fluorite is the mineral form of calcium fluoride, (CaF2). In the mining industry fluorite is often called "fluorspar."
Fluorite is deposited in veins by hydrothermal processes. In these rocks it often occurs as a gangue mineral associated with metallic ores.
Fluorite is also found in the fractures and cavities of some limestones and dolomites.
It is used in a wide variety of chemical, metallurgical and ceramic processes, however, optical, lapidary and other uses are also important. Acid grade (97% CaF2): The purest grades of fluorite are a source of fluoride for
hydrofluoric acid (HF) manufacture, which is the intermediate source of most fluorine-containing fine chemicals.
Ceramic grade (80 – 96% CaF2): used for the manufacture of ceramics, enamels, glasses and glass fibers.
Metallurgical grade (> 60% CaF2): used in the iron and steel industry.
Optical Grade Fluorite: Specimens of fluorite with exceptional optical clarity have been used as lenses. Fluorite has a very low refractive index and a very low dispersion. These two characteristics enable the lens to produce extremely sharp images. These lenses are used in optical equipment such as microscopes, telescopes and cameras
Lapidary Grade Fluorite:
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 33
5) Perlite:
Perlite is a water bearing natural glass
That contains Silica, Alumina, Iron, Titanium,
Calcium, Magnesium, Sodium and potassium
Oxides
5) Perlite: Perlite is an amorphous volcanic glass that has a relatively high water
content (i.e., typically formed of the hydration of obsidian).
It occurs naturally and has the unusual property of greatly expanding when
heated sufficiently.
It is an industrial mineral and a commercial product useful for its light
weight after processing.
Various grades resulting from differences in the degree of hydration.
Used primarily as an insulator with its high heat resistance and high sound absorption.
Used in fertilizer
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 35
6) Building Stones
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 36
Durability and hardness
Ease of quarrying
Color and aesthetic value
Impurities and other undesirables
These come from all geological environments.
The most important economic factor for building materials is that the material has to be close to where it is going to be used, as the highest cost is in its transportation.
Building stones are by far the lowest cost geological materials and their value is usually in the order of only a few dollars per ton
Building Stones may be:
i) Crushed rock (or Aggregate Stone): Natural aggregate (crushed stone, sand, and gravel) is the most commonly used building material, along with concrete which is derived from crushed limestone. Bricks are made from fine aggregate along with clay which acts as the binding material, and iron oxide minerals for colouration.
Aggregate is also used as a sub-surface lining on our roads.
Plaster is derived from crushed and refined gypsum.
Coarse and fine aggregates
Fillers
Proximity to market
Optimum targets for exploitation. ii) Dimension (or Ornamental) stones are much higher-value building material and are used as decorative
facings on buildings. Examples: Marble, Quartzite, Gneiss, Schist, Serpentinite, Slate, Migmatite. By far the most commonly used dimension stones are marbles.
Characteristics of Building stones
Rip-rap There are many techniques used for reducing the power of
waves before they erode a coastline.
• Rip-rap is a sheet of boulders used at the toe of a slope to add weight and break the force of the waves.
• Rip-rap is made of highly resistant rocks to physical and
chemical weathering, often Basalt, Gabbro, Dolerite, Quartzite, Granite, or Gneiss, which will not weather or
break down.
• Because the blocks are angular, they fit together tightly, but still allow water to drain through back to the sea.
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 37
The part of the coast was in the process of being reinforced with a wall of rip-rap. Beyond the wall was a grassy area with geotextiles and plants to reduce further the force of the waves.
RIP-RAP
Area of soft rocks which needed to be reinforced.
St Bees Head, Lake District
Geotextiles help to support the glacial till slope so that vegetation can establish itself.
Slope angle has been reduced
Rip-rap
Till cliffs
Rip-rap
Quartzite is highly resistant to physical and chemical weathering, so it does well in applications like this rip-rap
Introduction Sulfur (S) composes 0.06% of Earth’s crust
Sulfur (S) is an important constituent of volcanic gases, magmatic emanations, and is common in hot springs.
Elemental Sulfur is found on the Earth in:
Volcanic deposits or volcanic emanations (i.e., Fumaroles)
Underground deposits
On Earth, elemental sulfur can be found near hot springs and volcanic regions in many
parts of the world, especially along the Pacific Ring of Fire; such volcanic deposits are
currently mined in Indonesia, Chile, and Japan.
Sulfur is deposited from sulfates (SO4) and hydrogen sulfide (H2S) in bodies of water
where reducing conditions.
Sulfates (SO4) are also reduced by anaerobic bacterial (e.g., Clostridium nigrificans) to
hydrogen sulfide (H2S), which, in turn oxidises to sulfur (S) and water (H2O).
7) Sulfur Ore Deposits
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 41
Sulfur Reservoirs in Nature Sulfur (S) is distributed in the earth's crust in
the form of sulfates (SO4), sulfides, and native sulfur.
The largest physical reservoir is the Earth's crust where sulfur is found in gypsum (CaSO4.2H2O) and pyrite (FeS2).
The largest reservoir of biologically useful sulfur is found in the ocean as sulfate anions (2.6 g/L), dissolved hydrogen sulfide (H2S) gas, and elemental sulfur.
• Elemental sulfur was once extracted from salt domes where it sometimes occurs in nearly pure form, but this method has been obsolete since the late 20th century.
• Today, almost all elemental sulfur is produced as a by-product of removing sulfur-containing contaminants from natural gas and petroleum.
Sulfur also obtained from by-products of several industrial processes (H2S(g) from oil and natural gas deposits)
Sulfur powder
Roll Sulfur
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• Subsurface sulfur recovered by the Frasch Process: superheated water pumped down into deposit, melting the
sulfur and forcing it up the recovery pipe with the water
Frasch Process
Natural surface Sulfur Deposit
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 43
A Sulfur Deposit Melted sulfur obtained from surface
deposits by the Frasch process.
Figure 2 The Frasch Process for Recovering Sulfur from surface deposits
Important sedimentary sulfur deposits occur near Knibyshev, Sukeievo, and Chekur in Russia. The occurrences consist of thin gypsum beds with layers of pure sulfur, laminations of sulfur and calcite, or sulfur nodules in bituminous limestone. Celestite (SrSO4) is an unusual associate.
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 44
Sulfur Mining
Sulphur Mine, Kawah Ijen Volcano, Java, Indonesia
On Earth, elemental sulfur can be found near hot springs and volcanic regions in many parts of the world, especially along the Pacific Ring of Fire; such volcanic deposits are currently mined in Indonesia, Chile, and Japan.
A man carrying sulfur blocks from Kawah Ijen, a volcano in East Java, Indonesia, 2009
USAGE • Elemental sulfur is used in Black gunpowder, Matches, and Fireworks; in
the vulcanization of rubber; as a fungicide, insecticide, and fumigant; in the manufacture of phosphate fertilizers; and in the treatment of certain skin diseases.
• The principal use of sulfur, is in the preparation of its compounds, such as: Sulfuric acid. Sulfur dioxide, used as a bleaching agent, disinfectant, and
refrigerant; Sodium bisulfite, used in paper manufacture; carbon disulfide, an
important organic solvent; Hydrogen sulfide, sulfur trioxide, used as reagents in chemistry; Epsom salts (magnesium sulfate), used as a laxative, bath additive,
exfoliant, and magnesium supplement in plant nutrition; the numerous other sulfate compounds; and sulfa drugs.
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Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 46
The solution, transportation, and deposition of calcium and magnesium carbonate give rise to deposits of limestones, dolomite, and magnesite. The calcium is derived from the weathering of rocks and is transported to
the sedimentary basins chiefly as the bicarbonate, in part as carbonate, and as sulfate. Calcium carbonate (CaCO3) is deposited :
at all Eh conditions but mostly at higher pH values. by organic and mechanical means. by the photosynthesis of plants.
Carbon dioxide plays a dominant role in inorganic processes because the solution of the calcium carbonate in the sea is dependent upon it. If it escapes, calcium carbonate is precipitated Organic deposition is brought about by Algae, Bacteria, Morals, and Foraminifera.
Entire limestone beds may consist of Foraminifera or Nummulite shells, Coral, or larger fragmental shell formed mainly in shallow waters.
The deposition has been brought about by chemical precipitation with subsequent dehydration.
Ca2+ + CO32- CaCO3
8) Calcium Carbonate Deposits
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 47
Limestones Limestones
Limestones are non-clastic rock formed either chemically or due to precipitation of calcite (CaCO3) from organisms usually (shell) {Limestones are commonly containing abundant marine fossils}.
Limestones are the most common type of chemical sediment forming today by evaporation and biogenic processing of seawater.
Limestones are of marine or freshwater origin, and magnesium may in part replace the calcium, giving dolomitic limestones even though dolomite is also of primary origin. Impurities of silica, clay, or sand are commonly present, as well as minor amounts of phosphate, iron, manganese, and carbonaceous material.
Limestones formed by chemical precipitation are usually fine grained, whereas, in case of organic limestone the grain size vary depending upon the type of organism responsible for the formation Chalk: which is made up of Foraminifera is very fine grained Fossiliferous Limestone: which medium to coarse grained, as it is formed out of cementation of
Shells.
Coquina: larger fragmental shell formed mainly in shallow waters
Dolomite (or dolostone) is created by replacement of calcium by magnesium after shallow burial of limestone. Dolomite usually forms in tropical shallow marine environments.
Used Limestone, the source material for all lime based value added products – calcined. Limestone is widely used as a building construction material –concrete, blocks. Limestone is used in the manufacture - cement and glass. Limestone is used to strengthen and stabilize the sub-grade in road construction. Limestone is an alkali and is used extensively to neutralize acids – PH control. Paper, plastic, paint and rubber producers use calcium carbonate as a way to improve quality and lower
manufacturing costs.
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 48
Calcium Carbonate Deposits Non-fossiliferous Limestone Fossiliferous Limestone
Fossiliferous
Limestone
Non-fossiliferous
Limestone
Oolitic Limestone
Oolitic LS Dunes,
Bahamas
Biogenic Inorganic, ~clastic
Chemical and biochemical sedimentary Calcium Carbonate
Limestones – composed of calcite
Travertine Coquina
9) SILICEOUS SEDIMENTARY DEPOSITS (CHERTS)
Introduction Chert is the general term for very fine-grained, dense, very hard rocks and nonporous
sedimentary rocks that consist mostly or entirely of silica (SiO2), in the form of either amorphous silica or microcrystalline quartz presumably derived from recrystallization of amorphous silica. The crystal size of quartz in recrystallized chert is usually in the range 5–20 μm. Thin-section studies don’t help much because the quartz is too fine. Electron microscopy of fractured surfaces shows the quartz to be polyhedral, equant to
elongate, and closely fitted to surrounding grains. Cryptocrystalline geometries in the transition from amorphous silica to recrystallized quartz are complex.
Chert comes in two distinct varieties, nodular chert and bedded chert The relative importance of nodular chert and bedded chert has changed through
geologic time: bedded chert is much more common in the Precambrian, and nodular chert is more common in the Phanerozoic.
White and red chert interlayered with
hematite, Soudan Iron Formation
Chert nodules in Limestone
8) SILICEOUS SEDIMENTARY DEPOSITS (CHERTS)
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 52
Terminology Here are a few terms for kinds of amorphous silica and chert:
Amorphous silica:
material composed of relatively pure SiO2 but with only very local crystallographic order.
includes various kinds of hydrated and dehydrated silica gels, silica glass, siliceous sinter formed in hot springs, and (certainly of greatest
geological importance) the skeletal materials of silica-secreting organisms .
Opal (or opaline silica)
is a solid form of amorphous silica with some included water (i.e., hydrated metastable quartz that makes up tests of siliceous organisms).
is abundant in young cherts, back into the Mesozoic.
Its geological occurrence is by alteration of volcanic ash, precipitation from hot springs, and, by far most importantly, precipitation as skeletal material by certain silica-secreting organisms (see a later section).
Opal starts out as what is called Opal-A, which shows only a very weak x-ray diffraction pattern, indicating that any crystallographic order
is very local. With burial, during the initial stage of diagenesis, opal-A is transformed into Opal-CT, which shows a weak x-ray diffraction
pattern characteristic of cristobalite another silica mineral; see below). Upon further diagenesis, opal-CT is transformed into crystalline quartz, resulting in chart that consists of an equant mosaic of microquartz crystals. By that stage, most or all of the fossil evidence of origin
is obliterated.
Chalcedony (fibrous silica)
is a very finely crystalline form of silica consisting of radiating needles or fibers, often spherulitic, of quartz.
sheaf like bundles of radiating extremely thin crystals of about 0.1mm in length
There’s probably amorphous silica in among the needles, and a variable water content.
This stuff is metastable with respect to ordinarily crystalline quartz, but it hangs around a long time; it’s found even in Paleozoic cherts.
Granular microquartz: consists of nearly equi-dimentional grains of quartz. Grain sizes range from ~1 to 50 microns
Megaquartz: elongated grains greater than 20 microns in length.
Flint is the general-language equivalent of chert, usually applied to dark gray chert in nodules or as beds. The non-scientific equivalent term is flint.
Jasper: chert that’s red because it contains hematite (often more than a few percent).
Porcelanite (also spelled porcellanite): a minutely porous form of chert with a dull appearance on the fresh surface 6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 53
From Boggs, Principles of Sedimentology
and Stratigraphy, 4th ed., p. 214
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 54
Siliceous sediment experience a predictable transformation from amorphous opal to chalcedony and eventually to microcrystalline quartz due to time/temperature dependant chemical reaction
Microquartz and megaquartz
From Boggs, Principles of Sedimentology and Stratigraphy, 4th ed., p. 207, p209, P.210
Diatoms in deep sea sediment
Nodular chert
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1) Nodular Cherts
Nodular Chert; diagenetic origin (typical): Silica derived from the solution of siliceous fossil material in predominantly carbonate rich successions (Sponge spicules and other siliceous bioclasts)
are widespread as nodules in limestone.
Are more common in the Phanerozoic. are varied in shape, from more or less regular discoidal or egg-shaped bodies (that’s the common shape for relatively
small chert nodules) to highly irregular knobby and warty bodies (the common shape of relatively large chert nodules).
Their size ranges from a few centimeters to a few tens of centimeters.
tend to be concentrated along certain bedding planes. Where abundant, they often form a two-dimensionally or three-dimensionally interconnected network.
are usually structureless, but some show faint traces of stratification coincident with that in the enclosing limestone.
Origin: Although in the past some geologists believed that nodules form by direct precipitation of silica gel on the ocean bottom, today the evidence for a replacement origin is considered to be overwhelming:
irregular shape and interconnectedness of many nodules;
presence of irregular patches of limestone in nodules;
association of chert and silicified fossils in many limestones;
presence of replaced fossils in some nodules;
traces of bedding passing through nodules;
contacts of nodules passing through fossils.
Source of the silica: the nodules can be explained by the presence of abundant biogenic amorphous silica in the original sediment and then diagenetic reorganization.
By diagenetic reorganization is meant the process by which the disseminated bodies of opaline silica (sponge spicules, diatoms, radiolarians) are dissolved, whereupon the silica in solution migrates to certain places in the sediment where it is reprecipitated in the form of opal-CT to form the nodules. This happens because the pore fluids are undersaturated with respect to the original biogenic silica, which consists of opal-A, but are supersaturated with respect to opal-CT, which has lower solubility than opal-A.
Where the chert nodules form only a small part of the bulk volume of the rock, a good case can be made that the silica that forms the nodules was present in the sediment from the time of deposition. But how about when the chert forms the greater part of the rock? Then a stronger case could be made for introduction of silica in solution after deposition, by circulating pore solutions.
Chert varieties:
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 56
2) Bedded Cherts Chert is also found as continuous beds, from centimeters up to as much as a few meters thick, often,
but not always, interbedded with shale. Bedded cherts are also often interbedded with turbidite sandstones and submarine volcanics. Most such bedded cherts show abundant evidence of having been deposited in the deep ocean. Two
scenarios seem most attractive for explaining these cherts: Open-ocean siliceous ooze is conveyor-belted to subduction margins and incorporated into a
subduction mélange. Siliceous sediment is deposited near a subduction margin, interbedded with subduction-zone
volcanics . Here we need to distinguish between Phanerozoic bedded cherts and Precambrian bedded cherts.
Phanerozoic bedded cherts: usually contain radiolarians, and they can be explained by lithification and diagenesis of radiolarian-rich bottom sediments, although some may have been inorganically precipitated with radiolarians as a nonessential constituent.
Precambrian bedded cherts: show no convincing evidence of having started out as biogenic sediment, in as much as no
silica-secreting marine organisms are known from the Precambrian. Most Precambrian cherts seem have been inorganically precipitated, although the
processes involved are not entirely clear. It’s common; cherts interbedded with chemically precipitated Ironstones. Some of the very oldest sedimentary rocks, in greenstone terranes, are bedded cherts. Chert is characteristically interbedded, down to centimeter scale, with Precambrian Iron
Formations (Ifs).
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 57
Silica Geochemistry The solubility of quartz in pure water is very small, several parts per million.
Figure 1 shows a graph of quartz solubility as a function of pH. You can see that the solubility of quartz is very low for pH values up to about 8 (slightly alkaline) but then rises sharply with increasing pH. It’s hard to measure, but it can be calculated. Moreover, attainment of equilibrium is very slow.
The solubility of amorphous silica is an order of magnitude higher, and attainment of equilibrium is also slow, but much faster than for quartz. The dominant species of silica in solution in natural waters in the usual range of pH is silicic acid, H4SiO4, a weak acid. At room temperature and pressure, amorphous silica is metastable with respect to quartz, but precipitates formed from supersaturated solutions are always amorphous silica. This is because the building of the quartz crystal structure at low temperatures takes a very long time. Solutions unsaturated with respect to amorphous silica but supersaturated with respect to quartz remain stable for many years if not longer. Clear crystalline quartz can’t be precipitated in the laboratory at the low temperatures and pressure of sedimentary environments. Presumably nature can do it because of the longer times involved.
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 58
Pathways of silica transformation after
deposition
From Boggs, Principles of Sedimentology and Stratigraphy, 4th ed.,
p. 214
Silica stability vs. pH
From Boggs, Principles of Sedimentology and Stratigraphy,
4th ed., p. 214
Very low
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Sources of silica in marine water The concentrations of dissolved silica in rivers, streams, and lakes are a few tens of parts per million. Concentrations are also in this range in groundwater; the deeper the groundwater, the higher the silica
concentration. What are the sources of silica in solution? weathering of silicate minerals: this is the ultimate source of most of the silica in solution in the
Earth’s surface waters. thermal springs: the concentration of dissolved silica concentration is very high but the absolute
volume is small. dissolution of amorphous silica: this must be important in areas underlain by silica-containing
sedimentary rocks, but it is certainly not as important overall as weathering of silicates dissolution of quartz: most natural fresh waters are in the pH range for which the solubility of quartz
is very low, so dissolution of quartz is not an important source of silica in solution. Here’s the bottom line: it’s generally agreed that by far the greater part of dissolved silica comes from weathering of silicate minerals in source rocks.
The concentration of dissolved silica in the oceans is surprisingly and extremely small: only a few tenths of a part per million. In the present oceans, there’s no possibility of precipitating silica inorganically. The reason for this very low silica concentration in the oceans is that several kinds of organisms are very effective in extracting silica from sea water and fixing it in the form of opaline silica in their skeletons. They do this out of equilibrium, by metabolic concentration processes.
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 60
Origin of Chert
Extraction from seawaters
Inorganic extraction is unlikely in unsaturated
waters like those of the ocean. However, it may
be possible in local basin saturated in SiO2 due to
dissolution of volcanics.
Biogenic extraction appears to be the only large
scale mechanism for silica extraction from the
seawater. Diatoms are largely responsible during
the present, whereas radiolarians extracted more
during the Jurassic and earlier periods.
Nodular or other replacement chert are formed
during diagenesis where they replace carbonates
and clays.
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10) PHOSPHITE ORE DEPOSITS
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 62
Introduction Phosphorus is dissolved from the rocks, some of it enters the soil from which it is abstracted by
plants, from them passes into the bodies of animals, and is returned via their excreta and bones to
accumulate into deposits.
These in turn may undergo re-solution; reach the sea, and there the phosphorus deposited or
accumulated by sea life, embodied in sediments, and returned to the land upon uplift, when a new;
cycle may start.
Phosphates are soluble in carbonated water and, in the absence of calcium carbonate, will stay in solution. The phosphate in limestones resists solution.
Some phosphoric acid in reaches the sea, where it is extracted by organisms; some is re-deposited
as secondary phosphates, which may be re-dissolved; and some is retained in the soil.
Swamp waters rich in organic matter also dissolve phosphates, and some phosphorus compounds
are thought to enter solution as colloids.
Phosphorus is probably transported by streams as phosphoric acid and as calcium phosphate (some is transported by birds and animals).
Economic beds of phosphate are formed under marine conditions in the form of phosphorite.
The beds range in age from Cambrian to Pleistocene.
They are interstratified with other sediments and grade laterally into them.
Calcite and glauconite are usually found in the mineral paragenesis with phosphorite, occasionally
chlorite and siderite, and in the case of nodular deposits, also organic matter.
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Types of Phosphorite Deposits:
Phosphate deposits are of three main types:
1) Guano (or Guano Bird ; or Island Deposits): These are ancient and/or fossil deposits of bird or bat excreta.
Bird and bat excrement that has been leached to form an insoluble residue of calcium phosphate.
Guano deposits from birds are most commonly found on oceanic islands, especially abundant- like
some South Pacific Islands.
Guano deposits from bats are found in large cave systems.
Guano deposits need a dry climate for their preservation.
2) Igneous Phosphate deposits : Phosphate deposits are formed from alkaline igneous rocks such as nepheline syenites, carbonatites
and associated rock types. The phosphate is, in this case, contained within magmatic apatite, monazite or other rare-earth
phosphates. 3) Sedimentary Phosphate Deposits
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 64
Sedimentary Phosphorites
Mining guano in the Chincha Islands off the central coast of Peru ~1860
The nest of the Peruvian Booby is made of almost pure guano.
Igneous Phosphate deposits
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 65
Economic and potentially economic phosphate deposits of the world
www. Ifdc.org
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 66
3) Sedimentary Phosphate Deposits Sedimentary phosphorites are Organic/Chemical Sedimentary Rocks that contain more than 15% P2O5 or 6.5% phosphorus (P).
are mined from rocks, usually shales, dolomite, or limestones, that contain unusually high concentrations of the mineral apatite {Ca5(PO4)3(F, OH, Cl, ½ CO3)}. Sometimes it is mixed with enough calcite or clay to be limestone or shale.
Sometimes, this is nearly pure apatite, in which case it is called ―phosphorite” (i.e., Phosphorite is a commonly used term for lithified phosphate rock).
Immense quantities of phosphate rock or phosphorite occur in sedimentary shelf deposits, ranging in age from the Proterozoic to currently forming environments.
are commonly interbedded with marine shale, limestone, and dolomite.
have textures that resemble limestones.
may be made up of peloids, ooids, bioclasts and clasts that are now composed of apatite.
Common names: Rock phosphate, phosphates
Implies a marine origin
Form in restricted areas near continental margins: where deep ocean currents are upwelling.
Phosphorus is a limiting nutrient in many marine and fresh water ecosystems: limits primary productivity.
Very little phosphorus is supplied to the oceans by river inflow.
When phosphorus is supplied by upwelling from the deep ocean, productivity skyrockets.
A rain of phosphate-rich skeletal debris falls to the ocean floor.
Distinguished by chocolate brown color, may have pellets, lumps or nodules (mm scale)
Marine deposits often have nodules.
Deposits can be extensive (Ex: The Phosphoria Formation in Utah is phosphate-rich shale). Sedimentary phosphate deposits are of three main types:
a) Bone Beds (Bioclastic)
Composed largely of vertebrate skeletal fragments.
These are localized accumulations of fossil deposits of bone, teeth, scales and excreta (i.e. coprolites) that are occasionally thick enough to form economic deposits.
These have mostly been mined in the past. A good example of bone beds is the marsupial-rich bone phosphate deposits of the Wellington Caves near Dubbo, New South Wales.
b) Nodular:
Spherical to irregularly shaped nodules, with or without internal structure, often containing grain, pellets or fossils.
c) Pebble-bed:
The sandstone equivalent-composed of nodules, fragments or phosphatic fossils that have been mechanically concentrated by reworking of earlier formed phosphate deposits.
All marine sediments, particularly limestones, contain some phosphate, which under particular conditions may rise to a greater concentration than normal (phosphatic limestone), but rarely reaching an economically extractable concentration.
These deposits are rare and usually arise from either the leaching of the phosphatic limestone (dissolving away the calcium carbonate and leaving behind the detrital phosphate) or the extraction of phosphate at higher levels followed by secondary concentration from downward-percolating groundwaters
These deposits occur under relatively cool conditions in an oxygen-free environment.
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 67
Mineralogy and Mineral Composition of Sedimentary Phosphorite Deposits
The mineralogy of phosphate deposits is very complex. They usually consist of fine-grained mixtures of various calcium phosphates with the
most common mineral being varieties of apatite and related minerals {Ca5(PO4)3F}. Collophane is an amorphous calcium phosphate that is also commonly found in
phosphate deposits. Mineral composition of phosphorite deposits: is determined by the phosphorite
which is a composite chemical compound of calcium phosphate, calcium fluoride, and calcium carbonate of the type of nCa3(PO4)2.nCaF2.KCaCO3.
Three fractions can be distinguished:
1) fluor-apatite {3Ca3(PO4)2CaF2} 2) carbonate-apatite {3Ca3(PO4)2CaCO3}; and 3) hydroxyl-apatite {3Ca3(PO4)2Ca(OH)2}.
Most are carbonate hydroxyl fluorapatites (a.k.a.: francolite) (Ca10(PO4,CO3)6F2-3) in which up to 10% carbonate ions can be substituted for phosphate ions.
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 68
Amblygonite Lazulite Pyromorphite Vivianite Torbernite
Autunite Xenotime Monazite Turquoise
Variscite Apatite Herderite Wavellite
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 69
Phosphates form in shallow marine
environments where dissolved PO4-3 is carried
by upwelling of deep ocean water.
These areas are biologically productive -
many fossils are found, especially bone
material.
Inhibition of organic mater decay due to
reducing conditions at ocean floor.
Interstitial water exhalation
Phosphatization: where phosphate replaces
skeletal and carbonate grains during
diagenesis.
Origin of Phosphorites
From Boggs, Principles of Sedimentology and Stratigraphy, 4th ed.,
p. 229
Phosphate accumulation is associated with oceanic upwelling (cold, oxygen and nutrient rich bottom waters coming to the surface, as happens off Peru). Under such conditions, there is a great profusion of life, and consequently death. Organic remains (soft-body parts, bones, fecal matter)
sinks to the bottom. The great abundance of incoming organic matter may
overwhelm the ability of bottom organisms to consume this rain of food, and some goes undigested.
Under anaerobic conditions, the reduced organic matter remains.
Under slightly more oxidizing conditions, the reduced organic matter gets consumed, but the phosphate remains.
Under normal oxidizing conditions, the phosphate gets consumed or dissolved into seawater.
Figure Schematic illustration of processes that form phosphate deposits in the marine environment
Figure Schematic illustration of the formation of Phosphorites in areas of upwelling on the open ocean shelves.
Main features of a simplified genetical model for Egyptian phosphorites
Worldwide occurrence of phosphatic deposits
From Boggs, Principles of Sedimentology and Stratigraphy, 4th ed., p. 224
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World Phosphate Rock Production and Demand-World Phosphate
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 75
Use of Phosphate
• 90% of all phosphates is used as fertilizer, 10% used for animal feedstuff, detergents, food
and drink products, fire extinguishers, dental products, and surface treatment of metals.
• Phosphates were once commonly used in laundry detergent in the form trisodium
phosphate (TSP).
In agriculture, phosphate is one of the three primary plant nutrients, and it is a component of fertilizers. In former times, it was simply crushed and used as is, but the crude form is now used only in organic farming. Normally, it is chemically treated to make superphosphate, triple superphosphate, or ammonium phosphates, which have higher concentration of phosphate and are also more soluble, therefore more quickly usable by plants.
Phosphate compounds are occasionally added to the public drinking water supply to counter plumbosolvency.
The food industry uses phosphates to perform several different functions ( For example, in meat products, it solubilizes the protein). This improves its water-holding ability and increases its moistness and succulence. In baked products, such as cookies and crackers, phosphate compounds can act as part of the leavening system when it reacts with an alkali, usually sodium bicarbonate (baking soda).
Phosphate minerals are often used for control of rust and prevention of corrosion on ferrous materials, applied with electrochemical conversion coatings
Phosphoric acid and Chemical reagents
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 76
Relationship of Phosphate Rock and Phosphate Fertilizers
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 77
11) EVAPORITE DEPOSITS
EVAPORITE DEPOSITS Evaporite deposits are formed by evaporation of lake water or seawater.
Evaporite is a name for a water-soluble mineral sediment (i.e. chemical sediment) that result originally
precipitated from saline (brine) solutions concentrated and crystallization by solar evaporation from an
aqueous solution.
Evaporite deposits that are composed of minerals that originally precipitated from saline (brine) solutions
concentrated by solar evaporation.
Evaporite Considered as Inorganic/Chemical Sedimentary Rock types:
―Chemical‖: derived from the precipitation of dissolved minerals in water.
―Inorganic‖: minerals precipitate because of evaporation and/or chemical activity.
Evaporites form in a variety of settings:
Most evaporites are derived from bodies of sea water or a saline inland lake experiences net
evaporation, the concentration of the ions dissolved in that water rises until the saturation point of
various materials is exceeded, and minerals precipitate or crystallize.
There are two types of evaporite deposits: namely Buried evaporite deposits and Brine evaporite
deposits.
Brine Evaporite deposits (found??) in both Marine and Non-marine environments:
Minerals precipitated from ―super-saturated‖ saline water in enclosed basin environments under dry arid conditions with high evaporation rates (e.g., Playa lakes). Playa lake basins between mountain ranges, especially in Basin and Range Province.
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 79
Evaporation has been important in producing many valuable types of non-metallic mineral deposits.
Evaporites are excellent indicators of paleoclimate: it takes a hot and arid climate for major evaporite
deposits to form. Evaporite deposits are known from all the continents, with ages ranging from
Precambrian to Late Cenozoic (although Precambrian evaporites are scarce, either because they
were not deposited or because they have been dissolved away during diagenesis through geologic
time).
Extracted by Solution mining techniques (or Frasch Process)
Two wells
Selective dissolution
Hot leaching
1) Buried deposits : Evaporite deposits that formed during various
warming Seasonal and climatic change periods of
geologic times.
Like: Shallow basin with high rate of
evaporation – Gulf of Mexico, Persian Gulf, ancient Mediterranean Sea, Red Sea
The most significant known evaporite depositions happened during the Messinian salinity crisis in the basin of the Mediterranean
2) Brine deposits: Evaporite deposits that formed from evaporation:
Seawater or ocean (Ocean water is the prime source of minerals formed by evaporation) . Then, solutions derived
from normal sea water by evaporation are said to be hypersaline
Lake water
Salt lakes
Playa lake
Springs
Extracted by Normal evaporation techniques
Pond Marsh
Evaporite deposits
Brines form by strong evaporation. These ponds on the shores of Great Salt Lake are sources of magnesium as well as salt.
Water well drilling on the western portion of Allana Potash license, Dallol Project-Ethiopia
Potash salt and halite crystallization in pilot test evaporation ponds
KCl
The formation of the potash deposits (Barrier theory“)
Environments
Marine: Coastal Mud flats – Sabkhas Salt pans Barred basins
Continental: Salt lakes
Springs
ENVIRONMENTS FOR EVAPORITE PRECIPITATION
Volumetrically, each can be significant:
1) Coastal evaporites
Form in a Sabkha environment: A coastal, supratidal mudflat
Evaporites do not precipitate directly from seawater
Evaporites replace other material (mineral) in the shallow subsurface
Marine processes dominate
One of the most interesting areas to sedimentologists
Forms many oil traps
Also provides one model for dolomite formation
2) Eolian/interdune
Between sand dunes and ridges
3) Continental: Sabkha/playa
Shallow saline lakes
Note: these models don’t explain all evaporites
The importance of shallow vs. deep water is still debated
A problem: To deposit 2000 m of evaporite, you would need to evaporate a LOT of seawater!!
Ex: Evaporation of the entire Mediterranean Sea would only produce 60 m of evaporites
So: We need models or mechanisms that can replenish the supply of ions
The most significant known evaporite depositions happened during the Messinian salinity crisis in the basin of the Mediterranean.
Compared between Marine and Non-marine evaporites Marine evaporites Non-marine evaporites
Marine Environments:
Coastal
Mud flats – Sabkhas
Salt pans
Barred basins
can be described as ocean or sea water
deposits (solutions derived from normal sea
water by evaporation are said to be
hypersaline)
Shallow basin with high rate of evaporation:
e.g. Gulf of Mexico, Persian Gulf, ancient
Mediterranean Sea, and Red Sea.
The most important salts that precipitate from
sea water: Gypsum, Halite, and Potash salts
{Sylvite (KCl), Carnallite (KMgCl3 * 6H2O),
Langbeinite (K2Mg2(SO4)3), Polyhalite (K2Ca2Mg(SO4)6 *
H2O), Kanite (KMg(SO4)Cl * 3H2O), and Kieserite
(MgSO4)}
Marine evaporite deposits are widespread.
In North America, for example, strata of
marine evaporites underlie as much as
30% of the land area.
Marine evaporites produce:
Most of the salt that we use.
The gypsum used for plaster.
Continental Environments:
Salt lakes
Saline Inland lakes Playa lakes
Inland lakes
Groundwater Springs
Saline lakes includes things such as:
Perennial lakes, which are lakes that are there year-round;
or
Playa lakes, which are lakes that appear only during
certain seasons,
Examples of modern non-marine depositional environments
include the Great Salt Lake in Utah and the Dead Sea, which lies
between Jordan and Israel.
The layers of salts precipitate as a consequence of evaporation:
Salts that precipitate from lake water of suitable composition
include: Sodium carbonate (Na2CO3), Sodium sulfate
(Na2SO4), and Borax (Na2B4O7.1OH2O).
Borax and other boron-containing minerals are mined from
evaporite lake deposits in Death Valley and Searled and Borax
Lakes, all in California; and in Argentina, Bolivia, Turkey, and China.
Huge evaporite deposits of Sodium carbonate were laid down in the
Green River basin of Wyoming during the Eocene Epoch. Oil shales were also deposited in the basin.
The most important salts that precipitate from lake: Blödite, Borax
(Na2B4O7.1OH2O), Epsomite (MgSO4.7H2O), Gaylussite,
Glauberite, Mirabilite, Thenardite and Trona
(NaHCO3.Na2CO3.2H2O).
Non-marine deposits may also contain Halite, Gypsum, and
Anhydrite, and may in some cases even be dominated by these
minerals, although they did not come from ocean deposits.
Mediterranean Evaporates
Evaporation proceeds most rapidly in warm, arid climates. In the evaporation of bodies of saline water, concentration of the soluble salts occurs, and when super-saturation of any salt is reached, that salt is precipitated.
Deposition of minerals by evaporation is dependent on factors:
1) Solubility contents,
2) Temperature,
3) Pressure,
4) Depositional environment, and
5) Seasonal and climatic changes.
PROCESS OF MINERAL FORMATION BY
EVAPORATION
The potash and salt deposists worldwide
Quelle: K+S Käding/Beer
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 87
1) Chemistry of Seawater
The first step toward looking at evaporites
Source of evaporites: is seawater Ocean water is the prime source of minerals formed by
evaporation.
Dissolved Species - Seawater NaCl is most abundant because of compostion of seawater:
Includes all dissolved ions ~34.7 ppt
Most common ions: Cl-, Na+, Mg 2+, SO42-, Ca2+, K+...
Trace components: Br, F, B, Sr
85.65 % Na2+ and Cl- ions
remaining solutes 14.35%
About 3.45% of seawater consists of dissolved salts of which 99.7% by weight is made up of only seven, ions that are as listed below :-
These components of seawater can all contribute to evaporite mineralization.
Na+ 30.61 Cl- 55.04
Mg2+ 3.69 SO42- 7.68
Ca2+ 1.16 HCO3- 0.41
K+ 1.10
CHEMISTRY OF EVAPORITES
Dissolved Species - Rivers
• Main dissolved species in freshwater is Ca, CO3 and SiO4
6 November
2014
Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 88
Evaporation of Seawater In terms of volumes of precipitated salts, experiments like that show that if a column of sea water 1000 m thick is evaporated to dryness, the precipitated salt deposit would be about 17 m thick.
Of this, 0.6 m would be gypsum, 13.3 m would be halite, and the rest, 2.7 m, would be mainly salts of potassium and magnesium.
But is this how most evaporite deposits are formed?
1000 m (1 km) of seawater will produce
17 m of evaporites
ppt. sequence controlled by
solubility – least soluble first
0.1 m CaCO3
0.6 m gypsum
13.3 m NaCl
3 m KCl, KMgCl
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 89
Volume of
water
remaining Evaporite Precipitated
50%
At this point, minor carbonates
begin to form.
A little iron oxide and some
aragonite are precipitated.
Minor quantities of carbonate
minerals (Calcite and dolomite)
form.
a) Calcite(CaCO3):
Precipitates if < 50% of seawater is
removed.
Only accounts for a small % of the total
solids
20%
Gypsum precipitates:
Gypsum (<42°C) or Anhydrite
(>42°C).
b) Gypsum:
Precipitates if 80-90% of seawater has
been removed
Solution is denser
10% Rock salt (halite) precipitates
c) Halite:
Precipitates if 86-94% of original seawater
has been removed
Brine (solution) is very dense
5%
Mg & K salts precipitate
Precipitation of various
magnesium sulfates and chlorides,
and finally to NaBr and KCl.
Potassium and magnesium salts
(kainite, carnallite, sylvite)
d) Potassic salts:
Precipitate if > 94 % of original seawater
has been removed
So: ionic strength (potential) of
evaporating seawater has a strong control
over minerals that form
Inc
rea
sin
g E
va
po
rati
on
Ra
tes
The first phase
De
cre
as
ing
ord
er
of
so
lub
ilit
y
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 90
Economic importance of evaporites Halite- rock salt for roads, refined into table salt
Thick halite deposits are expected to become an important location for the disposal of nuclear waste because of their geologic stability, predictable engineering and physical behaviour, and imperviousness to groundwater.
Gypsum- Alabaster: ornamental stone; Plaster of Paris: heated form of gypsum used for casts, plasterboard, … etc.; makes plaster wallboard.
Potash- for fertilizer (potassium chloride, potassium sulfates)
Evaporite minerals, especially nitrate minerals, are used in the production on fertilizer and explosives.
Salt formations are famous for their ability to form diapirs, which produce ideal locations for trapping petroleum deposits.
Evaporite minerals start to precipitate when their concentration in water reaches such a level that they can no longer exist as solutes.
The minerals precipitate out of solution in the reverse order of their solubilities, such that the order of precipitation from sea water is
Calcite (CaCO3) and dolomite (CaMg(CO3)2)
Gypsum (CaSO4-2H2O) and anhydrite (CaSO4).
Halite (i.e. common salt, NaCl)
Potassium and magnesium salts
The abundance of rocks formed by seawater precipitation is in the same order as the precipitation given above. Thus, limestone (calcite) and dolomite are more common than gypsum, which is more common than halite, which is more common than potassium and magnesium salts.
Evaporites can also be easily recrystallized in laboratories in order to investigate the conditions and characteristics of their formation.
Major groups of evaporite minerals More than eighty naturally occurring evaporite minerals
have been identified. The intricate equilibrium relationships among these minerals have been the subject of many studies over the years. This is a chart that shows minerals that form the marine evaporite rocks, they are usually the most common minerals that appear in this kind of deposit.
Hanksite, Na22K(SO4)9(CO3)2Cl, one of the
few minerals that is both a carbonate and a
sulfate
Mineral
class
Mineral
name
Chemical
Composition Rock name
Halites
(or
Chlorides)
Halite NaCl Halite; rock-salt
Sylvite KCl
Potash Salts
Carnallite KMgCl3 * 6H2O
Kainite KMg(SO4)Cl * 3H2O
Sulfates
Polyhalite K2Ca2Mg(SO4)6 * H2O
Langbeinite K2Mg2(SO4)3
Anhydrate CaSO4 Anhydrate
Gypsum CaSO4 * 2H2O Gypsum
Kieserite MgSO4 * H2O --
Carbonates
Dolomite CaMg(CO3)2 Dolomite,
Dolostone
Calcite CaCO3 Limestone
Magnesite MgCO3 --
Calcium Sulfate Deposition
Calcium sulfate may be deposited either in the form of gypsum (<42°C) or anhydrite (>42°C), depending upon the temperature, pressure, and salinity of the solution.
Occurs as part of the evaporite succession (Sequence of formation of evaporites: Calcite dolomite gypsum halite sylvite Mg – salts).
The first salts to separate by the evaporation of seawater are carbonates.
When the water has been evaporated to about 20% of its original volume, calcium sulfate starts to separate. At the temperatures of evaporation of marine basins, much gypsum will always be deposited first if the temperature is <42°C, and that marine beds of pure anhydrite imply either that the early deposited gypsum was converted to anhydrite or that deposition occurred above the conversion temperature of >42°C.
Equilibrium temperature for the reaction CaSO4*2H2O CaSO4 + 2H2O(Liq. Sol.)
is a function of activity of H2O of the solution. Anhydrite can be hydrated back to gypsum
upon uplift and exposure to low-salinity surface waters.
Resulting Products.
Calcium sulfate deposition occurs in: 1) Beds of relatively pure gypsum or
anhydrite from a few meters to many hundreds of meters in thickness (gypsum beds constitute one of the most important nonmetallic resources and anhydrite finds little use);
2) Gypsum beds with impurities of anhydrite;
3) Alabaster, massive fine-grained white or lightly tinted variety of gypsum and
4) Gypsite, an admixture with dirt. 5) The beds are generally interstratified
with limestone or shale, and they are commonly associated with salt.
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 92
Gypsum Uses: Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate (CaSO4·2H2O).
Gypsum is used in a wide variety of applications:
Gypsum board is primarily used as a finish for walls and ceilings, and is known in construction as drywall, sheetrock or plasterboard.
Gypsum blocks used like cement blocks in building construction.
Plaster ingredient (surgical splints, casting moulds, modeling)
Plaster of Paris: heated form of gypsum used for casts, plasterboard, … etc.
Alabaster: ornamental stone
As alabaster, a material for sculpture, especially in the ancient world before steel was developed, when its relative softness made it much easier to carve.
A binder in fast-dry tennis court clay
Adding hardness to water used for brewing
Used in baking as a dough conditioner, reducing stickiness, and as a baked-goods source of dietary calcium. The primary component of mineral yeast food.
A component of Portland cement used to prevent flash setting of concrete
Soil/water potential monitoring (soil moisture)
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 93
Gypsum
Ca[SO4] · 2H 2O S.G. 2.312 - 2.322 Hardness 2 Color Colorless to white, often tinged other hues due to impurities; colorless in transmitted light.
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 94
Order of precipitation of common compounds 1) CaCO3 and MgCO3 are the 1st to precipitate
2) CaSO4 precipitates next (Calcium all precipitated). Leaving mostly Na and Mg cations
3) (Na2CO3) next in order precipitates if any CO3 left
4) (Na2SO4) precipitates next leaving mostly the chloride compounds
5) MgSO4 precipitates out all that is left is NaCl
6) NaCl saltern is left. These are fairly common (Great Salt Lake)
7) MgCl2 and CaCl2 lakes are rare (Called Bitterns Dead Sea).
8) If all water evaporates - bed of salt (NaCl) usually results.
Continental waters (saline lakes) and Inland brine lakes evaporation:
Epsomite {or Epsom salts} (MgSO4.7H2O
Borax (Na2B4O7·10H2O or Na2[B4O5(OH)4]·8H2O)
Trona (NaHCO3.Na2CO3.2H2O)
Natron (Na2CO2.10H2O)
Pre
cip
itati
on
seq
uen
ce
EVAPORATION SEQUENCE OF CONTINENTAL WATERS AND INLAND LAKES
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 95
Lakes Seawater
1) Calcite (CaCO3) and Magnesite (MgCO3) 1) Calcite(CaCO3) and Dolomite (CaMg(CO3 )2
2) Gypsum (CaSO4 *2H2O) precipitates next. 2) Calcium Sulfate precipitates next as Gypsum (<42°C) or Anhydrite (>42°C).
3) Na2CO3 (in form of Trona and Natron) next in order precipitates if any CO3 left
4) Na2SO4 (in form Hanksite [Na22K(SO4)9(CO3)2Cl]) precipitates next leaving mostly the chloride compounds
5) MgSO4 (in form of Epsom salts) precipitates out all that is left is NaCl
6) NaCl saltern is left. These are fairly common (Great Salt Lake)
3) Rock salt (halite) precipitates
Precipitates if 86-94% of original seawater has
been removed
Brine (solution) is very dense
7) MgCl2 and CaCl2 lakes are rare (Called Bitterns Dead Sea).
8) If all water evaporates - bed of salt (NaCl) usually results.
4) Potassic salts: Precipitate if > 94 % of original seawater has been
removed.
So: ionic strength (potential) of evaporating seawater
has a strong control over minerals that form.
Potassium and magnesium salts (Kainite, Carnallite, Sylvite)
Precipitation of various magnesium sulfates and chlorides, and finally to NaBr and KCl.
Compared between Evaporation Sequence of Seawater and Lakes
Inc
rea
sin
g E
va
po
rati
on
Ra
tes
D
ecr
eas
ing
ord
er
of
solu
bili
ty
The first
phase
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 96
Potash Deposition
Potassium is the seventh most common element occurring in the Earth’s crust, accounting for 2.4% of its mass.
Potassium present in most rocks and soils. Consequently, they are not common and important deposits.
Some of the world's supply of potash is derived from marine evaporates.
The world has an estimated 250 billion metric tons of K2O resources.
Occurrences: Sedimentary salt beds remaining from Ancient Inland Seas (evaporite deposits)
Evaporation of Salt lakes and Natural brines
Potash deposits, i.e. natural concentrations of raw potash, consist of potassium salt rock, predominantly made up of the potassium minerals:
Sylvite (KCl),
Carnallite (KMgCl3*6H2O),
Kainite (4KCl.4MgSO4.11H2O) and
Langbeinite (K2Mg2(SO4)3), or
Potassium-bearing salt solutions either underground or in salt lakes.
Flotation is one of the major methods to upgrade the potash. Normally fatty acids are used as collectors for flotation. This type of collectors is not suitable for the treatment of complex phosphate ores when calcite, dolomite present. Potash can be separated from halite by reverse flotation.
Potash is the most important source of potassium in fertilizers (potassium chloride, potassium sulfates)
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 97
Water well drilling on
the western portion of
Allana Potash license,
Dallol Project-Ethiopia
Potash salt and halite crystallization in pilot
test evaporation ponds
KCl
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 98
The formation of the potash deposits (Barrier theory―)
World Potash Mine Production 2003
012345
6789
10
Canada
Russia
Belaru
s
Germ
any
Isra
el
Jord
an
United S
tate
s
United K
ingdo
m
Spain
China
Chile
Brazil
Ukrai
ne
Mil
lion m
etri
c to
ns,
K2O
Source: IFA
% o
f to
tal
pro
duct
ion
78% of total K2O produced
33
17 15
13
0
5
10
15
20
25
30
35
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 99
Potash Deposits in Dead Sea K extracted from Dead Sea
The world‟s largest reserve of potash in
the form of salt solutions is the Dead Sea
(up to 1 billion tonnes of K2O), which has
been used for potash production since the
beginning of the 1930s.
contains an estimated up to 1 billion
tonnes KCl
Israel and Jordon represented 11% of
world production in 2003
Today DSW operates on the Israeli side
and APC on the Jordanian side
Arab Potash, the only producer in Jordan
is being privatized
Dead Sea Works (DSW), with production
in Israel and recent acquisitions in Spain
and UK is the world‟s 5th largest producer
K2O
pro
duct
ion, „0
00 t
0
500
1000
1500
2000
2500
1994 1996 1998 2000 2002
Israel Jordan
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 100
12) SELECTED SOME NON-METALLIC
METAMORPHIC DEPOSITS
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 101
Formation of Mineral Deposits by Metamorphism
• Several kinds valuable non-metallic mineral deposits are formed from rocks chiefly by Regional metamorphism (i.e.,
• The source materials are rock constitutes that have undergone recrystallization or recombination, or both of the rock making minerals).
Rarely, water or carbon dioxide has been added, but other new constituents are not introduced as they are in contact metasomatic deposits.
The enclosing rocks are wholly or in part metamorphosed: it is the rock metamorphism that has given rise to deposits.
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 102
Non-metallic Metamorphic Minerals • Apart from metasomatism, metamorphic rocks
are not major mineral resources. • The chief deposits thus formed are: Asbestos,
Graphite, Talc, Vermiculite, Soapstone, Garnet, Emerald, Kyanite, Wollastonite, Andalusite and Sillimanite.
• Specific metamorphic minerals: Kyanite and Wollastonite for refractories Garnet for abrasives
• Ornamental stone: Marble, Quartzite, Gneiss, Schist, Serpentinite, Slate, Migmatite.
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 103
12.1) Asbestos Deposits Cancer hazard
Asbestos – what is it? Asbestos is a commercial term: Any fibrous mineral utilized in an industrial process with a 3:1 length to width
“A commercial term applied to a group of highly fibrous silicate minerals that readily separate into long, thin, strong fibers of sufficient flexibility to be woven. . .”
A collective mineralogic term that describes a variety of certain silicates belonging to the serpentine and
amphibole mineral groups, which have crystallized in the asbestiform habit causing them to be easily separated
into long, thin, flexible, strong fibers when crushed or processed.
There are two main types of asbestos minerals:
A) Serpentine asbestos (or Chrysotile Asbestos)
B) Amphibole asbestos.
Asbestos is the name applied to six naturally occurring minerals that are mined from the earth: Chrysotile, Crocidolite, Asbestiform grunerite (Amosite), Anthophyllite asbestos, Tremolite asbestos and Actinolite asbestos. The nomenclature and composition of amphibole minerals should conform with International Mineralogical Association recommendations (Leake, B.E.,
Nomenclature of Amphiboles. American Mineralogist. Vol. 82, 1019 - 1037, 1997)
The different types of asbestos minerals are:
Serpentine group:
Chrysotile (White asbestos)
Amphibole group:
Amosite (Brown asbestos)- Grunerite
Crocidolite ( Blue asbestos) - Riebeckite
Anthophyllite
Tremolite
Actinolite
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 105
Chrysotile Mg6Si4O10(OH)8
Grunerite = Amosite [Fe2Fe2+5]Si8O22(OH)2
Riebeckite = Crocidolite Na2[(Fe, Mg)3Fe3+2] Si8O22(OH)2
Anthophyllite [Mg2Mg5]Si8O22(OH)2
Tremolite Ca2Mg5Si8O22(OH)2
Actinolite Ca2(Mg4.5-2.5Fe2+0.5-2.5)Si8O22(OH)2
Asbestos – what is it? Each of these six minerals included in OSHA‟s asbestos standard occurs in both an Asbestiform
and a Nonasbestiform variety.
Three of the six minerals have been given a different name for each of their two forms. Chrysotile
is the asbestiform variety of the serpentine minerals group. In this group antigorite is a common
nonasbestiform mineral. In the amphibole group, crocidolite is the asbestiform variety of
riebeckite; amosite is the asbestiform variety of “cummingtonite”-grunerite.
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 106
Naturally occurring fibrous silicate minerals:
Wide range of useful properties have led to it being used in many products since ancient times;
Was commercially mined in many countries: Canada, South Africa, Russia, Zimbabwe, China,
USA, Italy, Australia, Cyprus …etc.
Chrysotile is the most common asbestos mineral (~90% of asbestos mined)
Asbestiform Variety Nonasbestiform Variety
Chrysotile Antigorite
Crocidolite Riebeckite
Amosite Cummingtonite - Grunerite
Asbestiform Nonasbestiform
Chrysotile Antigorite
Crocidolite Riebeckite
Amosite
Asbestiform and Nonasbestiform Varieties
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 107
A) Serpentine Asbestos (or Chrysotile Asbestos ): Chrysotile (Mg6Si4O10(OH)8) asbestos occurs in serpentine that has been altered from ultrabasic
igneous rocks, such as peridotite or dunite or magnesian limestones or dolomite; the first yields 93 % of the world's asbestos supply.
In the ultrabasic occurrences, the fiber in lens like veinlets enclosed in serpentine and has three modes of occurrence:
i) Cross-fiber, with fibers normal to walls, their length begin the width of the veinlet, or less if they contain “partings";
ii) Slipper, parallel or oblique to the walls, and long but of poor quality;
iii) Mass-fiber, composed of a mass aggregate of interlaced, unoriented, or radiating fibers.
Chrysotile fibers range up to 10 to 12 cm in length, rarely 20 cm; most of them are less than 2 cm. Chrysotile may make up from 2 to 20 %t of the rock.
Origin of Chrysotile Asbestos
Chrysotile asbestos is confined entirely to serpentine and strictly speaking, is a fibrous variety of serpentine.
Serpentinization is an autometamorphic process, and in the ultrabasic rocks, such as dunite, serpentinization has proceeded along fractures.
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 108
B) Amphibole Asbestos : The amphiboles comprise the minerals: amosite,
crocidolite, termolite, actinolite and anthophyllite. The amphibole varieties, of which crocidolite and
amosite are the most important. These two minerals are found in slates, schists and
banded ironstones over are extensive belt in Transvaal and Cape Province of South Africa.
The crocidolite deposits are said to be the most extensive asbestos deposits in the world but only make up 3.5 % of the world's asbestos market.
They are in part associated with dolerite sills.
Tremolite Ca2Mg5Si8O22(OH)2
Anthophyllite [Mg2Mg5]Si8O22(OH)2
Riebeckite = Crocidolite Na2[(Fe, Mg)3Fe3+2] Si8O22(OH)2
Grunerite = Amosite [Fe2Fe2+5]Si8O22(OH)2
Actinolite Ca2(Mg4.5-2.5Fe2+0.5-2.5)Si8O22(OH)2
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 109
Serpentine Amphibole
Structure of
Asbestos Fibers
Crystalline structure – sheet silicate
‘Scroll-like’ structure
Fibers are less straight, more flexible
and less liable to split into finer
fibers compared to the amphiboles
Crystalline structure – chain silicate
Different amphiboles distinguished by
variations in chemical composition.
Fibers are generally straighter, more
brittle and split into finer fibers more
readily than serpentine
Asbestiform Variety Chrysotile Crocidolite; Amosite
Nonasbestiform
Variety
Antigorite Riebeckite; Cummingtonite - Grunerite
Asbestos Minerals Chrysotile - White asbestos
Amosite - Brown asbestos (Grunerite) Crocidolite - Blue asbestos
(Riebeckite) Anthophyllite Tremolite Actinolite
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 110
Properties of Asbestos Fibres Industrial applications of asbestos take advantage of
a combination of properties:
Use of fibre as reinforcing material largely dependent on length of fibre,
Other properties that make asbestos useful include: Flexibility
High tensile strength
Non-combustibility
Resistance to heat
Low electrical conductivity
Resistance to chemical attack
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 111
Uses of Asbestos Widespread uses of asbestos include:
Thermal and acoustic insulation Spray coating (as fire protection) Fireproofing Artificial fireplaces and materials Asbestos reinforced building board Re-enforcing concrete, tiles Asbestos reinforced cement products Plastic products (e.g. vinyl floor tiles) Textiles Brake linings Pot holders and ironing board pads Patching and spackling compounds Wall and ceiling panels Pipe and duct insulation Building insulation Friction materials (brake pads …etc) Gaskets and packing materials Roofing felts, Roofing materials. … etc
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 112
12.2) Graphite Graphite or “Black Lead"
is soft and black, has a greasy feel, and marks paper; hence the term graphite (to write). Graphite is one of the allotropes of carbon. Unlike diamond, graphite is an electrical conductor. Graphite holds the distinction of being the most stable form of solid carbon ever discovered.
True graphite yields graphitic acid when treated with nitric acid; amorphous carbon does not. Synthetic graphite (i.e., produced from oil and anthracite coal,- new accounts for 90 % of the graphite
production). Occurrence:
Graphite occurs chiefly in metamorphic rock produced by regional or contact metamorphism. It is found in marble, gneiss, schist, quartzite and altered coal beds; It also occurs in igneous rocks, veins and pegmatite dikes. It may be considered the highest grade of coal, just above anthracite and alternatively called meta-anthracite,
although it is not normally used as fuel because it is hard to lignite. Most of the crystalline variety occurs in minute flakes disseminated through metamorphic rocks. The amorphous
variety is dust like form. The deposits may be of large size, and the graphite content may be as much as 7 %. Associated minerals are quartz, chlorite, rutile, titanite and sillimanite. Natural Graphite Occurrences as :
i) Dissemination ii) Fissure veins
Classification of Graphite:
There are three principal types of natural graphite, each occurring in different types of ore deposit: i) Crystalline flake graphite : (53%) occurs as isolated, flat, plate-like particles with hexagonal edges if unbroken
and when broken the edges can be irregular or angular (e.g., Madagascar-open pit, 410-950 $/t) ii) Amorphous graphite: occurs as fine particles, a noncrystalline, impure variety. It is debatable that the material
of graphitic slate, which yields "amorphous graphite", is really graphite or amorphous carbon. (e.g., Mexico-Underground mines, 240-260 $/t).
iii) Lump graphite (also called vein graphite): occurs in fissure veins or fractures and appears as massive platy intergrowths of fibrous or acicular crystalline aggregates, and is probably hydrothermal in origin (Sri Lanka-Underground mines).
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 113
USAGE Major uses:
Refractories: (High temperature applications- Melting Point 3927°C): Course flakes.
Steel Making: Amorphous graphite or fine flakes.
Expanded Graphite: Flakes.
Minor uses:
Trucks: Substitute for asbestos.
Foundry Facing and Lubricants: Amourphous or fine flakes are used High temperature dry lubricant.
Pencil Lead: Powder graphite + clay.
Zn-C Batteries: Powdered fine flaked graphite.
Electric Motor Brushes: Powder graphite.
Brike Lining/Shoes for Heavy: Made from amorphous or fine flakes
Graphite (Carbon), Fibers/Nanotubes: Reinforced/antistatic/ conductive plastics/ concreates/ rubbers.
Origin.
Graphite originates by
(1) Regional metamorphism;
(2) Original crystallization from igneous rocks as shown by its occurrence in granite, syenite and basalt;
(3) Contact metamorphism (i.e., as at Calabogie, Ontario, where its occurs with contact metamorphic silicates in limestone adjacent to an igneous intrusion); and
(4) Introduction by hydrothermal solutions, which accounts for vein deposits and as Beverly considers, for deposits in pegmatites and shear zones in schist.
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 114
12.3) Talc Formation: Talc, Soapstone , and Pyrophyllite Talc a product of metamorphism, is a hydrous magnesium silicate [Mg3Si4O10(OH)2], which when finely ground, forms the
familiar talcum powder.
There are three main types of talc:
i) Talc steatite: Trade name used to describe pure, soft, massive, compact varieties of talc.
ii) Fibrous talc
iii) Agalite: A special name applied to fibrous talc from New York State. Soapstone is a soft rock composed essentially of talc , with varying amounts of chlorite, micas, serpentine, magnesite,
antigorite and enstatite and perhaps some quartz, magnetite or pyrite. It is a massive, impure talcky rock that can be quarried and sawed into large blocks. Soapstone is typically gray, bluish, green or brown in color, often variegated.
Pyrophyllite {Al2Si4O10(OH)2}; occurs in phyllite and schistose rocks, often associated with kyanite, of which it is an alteration product. It also occurs as hydrothermal deposits. Typical associated minerals include: kyanite, andalusite, topaz, mica and quartz. Pyrophyllite serves some of the same uses as soapstone.
Occurrence : Commercial talc and soapstone depsotis occur in metamorphosed ultrabasic intrusives or dolomitic limestones. They are thus restricted to metamorphic area and are largely confined to the Precambrian. The best quality talc comes from metamorphosed dolomite limestones is generally associated with termolite, actinolite and
related minerals. These deposits are generally lens shaped in beds and reach widths up to 40 m. The important deposits of Ontario, New York, North Carolina, Georgia, California, Bavaria and Austria are of this type (i.e.,
metamorphosed dolomite limestones ). Origin:
Talc is an alteration product of original or secondary mangnesian minerals of rocks. It results from mild hydrothermal metamorphism, perhaps aided by simple dynamic metamorphism but never from
weathering. It is pseudomorphic after minerals such as termolite, actinolite, enstatite, diopside, olivine, serpentine, chlorite, epidote
and mica. It may be formed from any magnesian amphibole or pyroxene acted on by CO2 and H2O according to the reaction:
4MgSiO3 + CO2 + H2O Mg3Si4O10(OH)2 + MgCO3 It thus originates in:
i) regionally metamorphosed limestones, ii) altered ultrabasic igneous rocks ; and iii) contact metamorphic zones adjacent to basic igneous rocks.
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 115
Talc
Mg3Si4O10(OH)2
Hardness 1 (softest mineral)
S.G. 2.58 - 2.83
Color Colourless, white, pale green;
bright emrald-green to dark green,
brown, gray; Greasy feel
6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 116
Uses Talc is used in the production of ceramics (the main domestic use),
paint, as a filler in paper manufacture (for improving several paper
qualities and in recycling processes), plastics (as a functional filler,
providing rigidity to the plastic), paint and coatings, roofing, rubber,
food, electric cable, pharmaceuticals, cosmetics (talcum powder),
flooring, caulking, and agricultural applications.
Thus, talc is a part of everyday life.
Talc is used in baby powder, an astringent powder used for
preventing rashes on the area covered by a diaper. It is also often
used in basketball to keep a player's hands dry. Most tailor's
chalk, or French chalk, is talc, as is the chalk often used for
welding or metalworking.
Talc is also used as food additive or in pharmaceutical products
as a glidant. In medicine talc is used as a pleurodesis agent to
prevent recurrent pleural effusion or pneumothorax.
Talc is widely used in the ceramics industry in both bodies and
glazes. In low-fire artware bodies it imparts whiteness and
increases thermal expansion to resist crazing. In stonewares,
small percentages of talc are used to flux the body and therefore
improve strength and vitrification. It is a source of MgO flux in high
temperature glazes (to control melting temperature). It is also
employed as a matting agent in earthenware glazes and can be
used to produce magnesia mattes at high temperatures.
Talc is used as a filler, coating, pigment, dusting agent and extender in plastics, ceramics, paint, paper, cosmetics, roofing, rubber and many other products.
Data from the United States Geological Survey
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Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 117
Pyrophyllite
Al2Si4O10(OH)2
Same thing as Talc with Al instead of Mg
Hardness 1 - 2
S.G. 2.65 - 2.9
Color White, gray, pale blue, pale green,
pale yellow, brownish green
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Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 118
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12.4) Ornamental Metamorphic stones Formed by Contact / regional and Metasomatic processes
e.g., Marble, Quartzite, and Serpentinite
Marble and quartzite may be either regional or contact metamorphic.
Marble may also involve metasomatism.
Serpentinite is formed by metasomatic alteration of ultramafic-mafic rocks.
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Use of Marbles and Serpentinite Marble and Serpentinite are used as a decorative stone, and the
presence of cavities is often undesirable. For decorative purposes, the cavities may be filled with epoxy
colored to match the background color of the marble. Use of Quartzites
Quartzite is highly resistant to physical and chemical weathering, so it does well in applications like this Rip-rap.
120
12.4.1) Marble Marble is usually the product of metamorphism of limestone or dolomitic limestone. White marble is often dolomitic limestone. Limestones often contain silicate impurities, and the impurities may be converted to minute
crystals of sericite, chlorite, …..etc These crystals may impart a slightly silky luster to the marble, similar to the process that occurs
during the formation of phyllite.
Metamorphic Grade of Marble
Marbles range in grade from slates to schists.
Foliation may be visible in hand specimen:
Foliation may be due to plastic flow during metamorphosis, or
Foliation may be relict sedimentary.
Naming Marble
• Marbles may be named for their color (for example: pink marble, black marble, or white marble).
• Marble may also be named for accessory minerals such as brucite
(Mg(OH)2), grunerite, ….etc
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Relict sedimentary bedding in marble
Nonfoliated pink Marble
• Marble, CN
• The photo shows strongly twinned
and highly cleaved calcite
Brecciated Marble with Angular
fragments in carbonate matrix
Close up of brucite (Mg(OH)2)
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Cavities in Marble
The metamorphic process often releases large quantities of CO2.
This gas escapes though the marble and may lead large fractures and cavities in
the rock, in a manner similar to the formation of vesicular basalt.
Mineralogy of Marble
Common non-carbonate minerals in marble include: tremolite, actinolite, diopside,
epidote, phlogopite, scapolite, and serpentine
Epidote (along with albite) occur in lower grade marbles
Sphene, apatite, and scapolite are present in amphibolite facies marbles.
High-Grade Marble Mineralogy
Hornblende, plagioclase, and diopside are common; together with some mica in
the higher grade metamorphism
Under higher grade conditions, dolomite will disappear. Dolomite decomposes to
yield periclase (MgO) or brucite (Mg(OH)2).
Dolomite present in high-grade metamorphics is probably due to retrogressive
metamorphism.
Using:
Marble is used as a decorative stone, and the presence of cavities is often undesirable.
For decorative purposes, the cavities may be filled with epoxy colored to match the background color of the marble.
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12.4.2) Quartzite • Quartzites are often the metamorphic product of quartz sandstones • During metamorphism, the quartz grains become interlocking due to
compression and recrystallization. • If shearing forces are large enough, the quartz grains elongate and
interlocking grain boundaries granulate. • The granulation of the boundaries can only be seen in thin section. • In highly sheared quartzites, the quartz grains become lenticular.
• Sioux Quartzite, South Dakota
• Nonfoliated
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12.4.3) Serpentinite
• Serpentinite marble; Nonfoliated
• Serpentinite from California Mother Lode country, in the Sierra Nevadas
• Metallic mineral appears to be pyrite
Product of metasomatic alteration of ultramafic igneous rocks.
Serpentine minerals are usually pseudomorphous after the minerals they replace.
Serpentines replacing olivine even retain the irregular curving fractures typical of olivine.
The fractures may fill with very fine-grained magnetite produced during the serpentinization process.
Resulting structures are unusual, possibly due to volume expansion during metasomatism.
Slickensides are sometimes seen on serpentinites
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Serpentine are hydrous magnesium iron phyllosilicates ((Mg, Fe)3Si2O5(OH)4), chrysotile and picrolite and are of the same composition as serpentine.
Magnesite, in minute grains, inevitably accompanies the serpentine minerals - magnesite is a product of the metasomatic alteration
Other minerals found in serpentinites include tremolite, talc, and anthophyllite, usually as fibers or prisms on the borders of former olivine crystals.
Serpentinite Mineralogy