(1) Minerals and Rocks

What do all minerals have in common?

All minerals:1. occur naturally2. are inorganic.3. are solid.4. are elements or compounds with a unique

chemical makeup5. are made up of particles that are arranged in

a pattern that is repeated over and over (called a CRYSTAL)

What is a Mineral?A mineral is any naturally-

occurring, inorganic solid

that has a definite chemical

composition and a distinctive

internal crystal structure.

Mineral GroupsMinerals are grouped by the

elements they are made of.

Amethyst

Emerald Calcite

Mineral Group Characteristics Examples

Silicates

•Contain oxygen & silicon

•The most abundantgroup of minerals

Quartz, mica

MICA

Quartz


Non-Silicates

•Make up only 5% of the Earth’s crust

•Include some of the most important minerals

iron, copper, gold, silver, diamonds, rubies

GoldRuby Copper


Carbonates •Carbon & oxygen and a positive ion, such as calcium

Calcite (CaCO3)

Calcite with Duftite inclusions


Oxides Metallic ion and oxygen

Hematite (Fe2)O3


Sulfides Sulfur and a metallic ion

Pyrite (FeS2)

Galena (PbS)


Halides Halogens Fluorite (CaF)

Halite (NaCl)


Sulfates Metallic ion, Sulfur & oxygen

Barite (BaSO4)

Barite on CalciteBaSo4 / CaCO3

Barite

BaSo4


Native Elements Single elements Gold (Au), Silver (Ag)

http://www.gc.maricopa.edu/earthsci/imagearchive/gold.jpg

http://www.gc.maricopa.edu/earthsci/imagearchive/gold.jpg

Physical Properties of Minerals(can be used to identify the mineral)

1.Color• Can be misleading

• Can vary with the type of impurities

2. Luster• Surface reflection

• metallic = shiny like

metal

• nonmetallic = dull,

non-shiny surface

Pyrite has a metallic luster

Calcite has a nonmetallic luster

Luster

- is independent of

color; minerals of the

same color may have

different lusters, and

minerals of the same

luster may have

different colors.

Pyrite has a metallic luster

Calcite has a nonmetallic luster

3. Streak

• The color of the

powdered form of the

mineral

• Minerals must be softer

than the streak plate

• The streak is constant for

different samples of the

same mineral.

Streak…can help identify quartz

4. Hardness• The resistance of a mineral to being scratched

or its ability to scratch other minerals.

Mohs Hardness Scale

• Scale from 1 (softest) to 10 (hardest)

• Tested by using different objects (like human fingernail, copper, penny, glass, steel file)

5. Cleavage & FractureCleavage— tendency of a

mineral to break along

planes of weak bonding

Fracture— describes the

quality of the cleavage

surface

Other Properties

–Attraction to magnets

–Bending of light

–Reaction with hydrochloric acid

– Smell & taste

What is a gem?•A mineral or rock that is RARE and has a

VALUE

What is a Rock?• Naturally-occurring mixtures ofminerals, mineraloids, glass ororganic matter.

What is the difference

between a rock and a

mineral?

•ROCKS are made up of one or more MINERALS.

• Rocks are divided into 3 groups based on how they were formed:

•IGNEOUS•SEDIMENTARY•METAMORPHIC

Igneous Rock

Igneous rocks are called

fire rocks and are formed

either underground or

above ground.

Volcanic or extrusive

igneous rocks

Plutonic or intrusive

igneous rocks

Mineral Composition:

Granitic (felsic) ~ rocks with light-coloredsilicates (feldspar and quartz).

Basaltic (mafic) ~ contains dark silicateminerals and calcium-rich plagioclasefeldspar with no quartz.

~ with magnesium and iron

Andesitic ~ intermediate composition

Andesite is a fine-grained, extrusive igneous rock composed mainly of plagioclase with

other minerals such as hornblende, pyroxene and biotite. The specimen shown is

about two inches (five centimeters) across.

Basalt is a fine-grained, dark-colored extrusive igneous rock composed mainly of

plagioclase and pyroxene. The specimen shown is about two inches (five

centimeters) across.

Diorite is a coarse-grained, intrusive igneous rock that contains a mixture of feldspar,

pyroxene, hornblende and sometimes quartz. The specimen shown above is about

two inches (five centimeters) across.

Gabbro is a coarse-grained, dark colored, intrusive igneous rock that contains feldspar,

augite and sometimes olivine. The specimen shown above is about two inches (five


Granite is a coarse-grained, light colored, intrusive igneous rock that contains mainly

quartz and feldspar minerals. The specimen above is about two inches (five


Obsidian is a dark-colored volcanic glass that forms from the very rapid cooling of

molten rock material. It cools so rapidly that crystals do not form. The specimen

shown above is about two inches (five centimeters) across.

Pegmatite is a light-colored, extremely coarse-grained intrusive igneous rock. It forms near the

margins of a magma chamber during the final phases of magma chamber crystallization. It

often contains rare minerals that are not found in other parts of the magma chamber. The

specimen shown above is about two inches (five centimeters) across.

Peridotite is a coarse-grained intrusive igneous rock that is composed almost entirely of olivine.

It may contain small amounts of amphibole, feldspar, quartz or pyroxene. The specimen


Pumice is a light-colored vesicular igneous rock. It forms through very rapid solidification

of a melt. The vesicular texture is a result of gas trapped in the melt at the time of

solidification. The specimen shown above is about two inches (five centimeters)

across.

Rhyolite is a light-colored, fine-grained, extrusive igneous rock that typically contains

quartz and feldspar minerals. The specimen shown above is about two inches (five


Scoria is a dark-colored, vesicular, extrusive igneous rock. The vesicles are a result of trapped

gas within the melt at the time of solidification. It often forms as a frothy crust on the top of a

lava flow or as material ejected from a volcanic vent and solidifying while airborne. The


Welded Tuff is a rock that is composed of materials that were ejected from a volcano,

fell to Earth, and then lithified into a rock. It is usually composed mainly of volcanic

ash and sometimes contains larger size particles such as cinders. The specimen


Earth’s external process:

1. Weathering – disintegration and decomposition

of rock at or near Earth’s surface.

2. Mass wasting – transfer of rock material

downslope under the influence of gravity.

3. Erosion – incorporation and transportation of

material by a mobile agent usually water, wind,

or ice.

Sedimentary Rock

Little pieces of our earth have

been eroded--broken down and

worn away by wind and water.

Layer after layer of eroded

earth is deposited on top of

each.

Layers are pressed down more

and more through time, until the

bottom layers slowly turn into

rock.

Breccia is a clastic sedimentary rock that is composed of large (over two millimeter diameter)

angular fragments. The spaces between the large fragments can be filled with a matrix of

smaller particles or a mineral cement which binds the rock together. The specimen shown

above is about two inches (five centimeters) across.

Chert is a microcrystalline or cryptocrystalline sedimentary rock material composed of silicon

dioxide (SiO2). It occurs as nodules and concretionary masses and less frequently as a

layered deposit. It breaks with a conchoidal fracture, often producing very sharp edges.

Early people took advantage of how chert breaks and used it to fashion cutting tools and

weapons. The specimen shown above is about two inches (five centimeters) across.

Coal is an organic sedimentary rock that forms mainly from plant debris. The plant debris

usually accumulates in a swamp environment. Coal is combustible and is often mined

for use as a fuel. The specimen shown above is about two inches (five centimeters)

across.

Conglomerate is a clastic sedimentary rock that contains large (greater then two

millimeters in diameter) rounded particles. The space between the pebbles is

generally filled with smaller particles and/or a chemical cement that binds the rock

together. The specimen shown above is about two inches (five centimeters) across.

Limestone is a rock that is composed primarily of calcium carbonate. It can form organically from

the accumulation of shell, coral, algal and fecal debris. It can also form chemically from the

precipitation of calcium carbonate from lake or ocean water. Limestone is used in many ways.

Some of the most common are: production of cement, crushed stone and acid neutralization.

The specimen shown above is about two inches (five centimeters) across.

Sandstone is a clastic sedimentary rock made up mainly of sand-size (1/16 to 2

millimeter diameter) weathering debris. Environments where large amounts of sand

can accumulate include beaches, deserts, flood plains and deltas. The specimen


Shale is a clastic sedimentary rock that is made up of clay-size (less then 1/256

millimeter in diameter) weathering debris. It typically breaks into thin flat pieces. The


Siltstone is a clastic sedimentary rock that forms from silt-size (between 1/256 and 1/16

millimeter diameter) weathering debris. The specimen shown above is about two

inches (five centimeters) across.

Metamorphic Rock

• Metamorphic rocks are

rocks that have

"morphed" into another

kind of rock.

• These rocks were once

igneous or sedimentary

rocks.

• How do sedimentary and

igneous rocks change?

Agents of Metamorphism:

Heat – provides the energy to drive chemical

reactions that result in the recrystallization of

minerals.

Pressure – force per unit area.

Chemically active fluids – enhance the

metamorphic process, most commonly water

containing ions in solution.

Metamorphic rocks are classified

as:

Foliated ~ banded appearance that results

when minerals of a rock are brought into

parallel alignment.

Nonfoliated ~composed of only one mineral

that forms equidimensional crystals.

Amphibolite is a non-foliated metamorphic rock that forms through recrystallization

under conditions of high viscosity and directed pressure. It is composed primarily of

amphibole and plagioclase, usually with very little quartz. The specimen shown above

is about two inches (five centimeters) across.

Gneiss is foliated metamorphic rock that has a banded appearance and is made up of

granular mineral grains. It typically contains abundant quartz or feldspar minerals.

The specimen shown above is about two inches (five centimeters) across.

Hornfels is a fine-grained nonfoliated metamorphic rock with no specific composition. It

is produced by contact metamorphism. Hornfels is a rock that was "baked" while near

a heat source such as a magma chamber, sill or dike. The specimen shown above is


Marble is a non-foliated metamorphic rock that is produced from the metamorphism of

limestone. It is composed primarily of calcium carbonate. The specimen shown above

is about two inches (five centimeters) across.

Phyllite is a foliate metamorphic rock that is made up mainly of very fine-grained mica.

The surface of phyllite is typically lustrous and sometimes wrinkled. It is intermediate

in grade between slate and schist. The specimen shown above is about two inches

(five centimeters across).

Quartzite is a non-foliated metamorphic rock that is produced by the metamorphism of

sandstone. It is composed primarily of quartz. The specimen above is about two

inches (five centimeters) across.

Schist is metamorphic rock with well developed foliation. It often contains significant

amounts of mica which allow the rock to split into thin pieces. It is a rock of

intermediate metamorphic grade between phyllite and gneiss. The specimen shown

above is a "chlorite schist" because it contains a significant amount of chlorite. It is


Slate is a foliated metamorphic rock that is formed through the metamorphism of shale. It

is a low grade metamorphic rock that splits into thin pieces. The specimen shown

above is about two inches (five centimeters) across.

Once a rock is

formed, does it stay

the same rock

forever?

• Rocks are continually changed by

many processes, such as weathering,

erosion, compaction, cementation,

melting, and cooling.

• Rocks can change to and from the

three types.

What is the process through which rocks change?

The Rock Cycle

(1) Minerals and Rocks

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