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Clay MineralsSoils to Engineering Technology to Cat Litter

Clay MineralsClay minerals likely are the most utilized minerals … not just as the soils thatgrow plants for foods and garment, but a great range of applications, including oilabsorbants, iron casting, animal feeds, pottery, china, pharmaceuticals, drillingfluids, waste water treatment, food preparation, paint, and … yes, cat litter!

Bentonite workings, WY

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Clay MineralsThere are four main groups of clay minerals:

Kaolinite group - includes kaolinite, dickite, nacrite, and halloysite; formedby the decomposition of orthoclase feldspar (e.g. in granite); kaolin is theprincipal constituent in china clay.

Illite group- also includes hydrous micas, phengite, brammalite, celadonite,and glauconite (a green clay sand); formed by the decomposition of somemicas and feldspars; predominant in marine clays and shales.

Smectite group- also includes montmorillonite, bentonite, nontronite,hectorite, saponite and sauconite; formed by the alteration of mafic igneousrocks rich in Ca and Mg; weak linkage by cations (e.g. Na+, Ca++) results inhigh swelling/shrinking potential

Vermiculite-

Clay Minerals are Phyllosilicates

All have layers of Si tetrahedra

and layers of Al, Fe, Mg octahedra, similarto gibbsite or brucite

SEM view of clay

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Clays

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Clay Minerals

The kaolinite clays are 1:1phyllosilicates

The montmorillonite and illiteclays are 2:1 phyllosilicates

1:1 and 2:1 Clay Minerals

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Marine ClaysClays mostly form on land but are often transported to theoceans, covering vast regions.

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Kaolinite Al2Si2O5(OH)2

Kaolinite clays have long been used inthe ceramic industry, especially in fineporcelains, because they can be easilymolded, have a fine texture, and arewhite when fired.

These clays are also used as a filler inmaking paper.

In the United States, deposits are foundprimarily in Georgia, North Carolina,and Pennsylvania; china clay is alsomined in England (Cornwall) and France.

Kaolinite

Kaolinite is the purest ofclays, meaning that itvaries little in composition.It also does not absorbwater and does not expandwhen it comes in contactwith water. Thus,kaolinite is the preferredtype of clay for theceramic industry.

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Illite Illite is similar to muscovite andis the most common claymineral, often composing morethan 50 percent of the clay-mineral suite in the deep sea.

They are characteristic ofweathering in temperateclimates or in high altitudes inthe tropics, and typically reachthe ocean via rivers and windtransport.

Relict zircon in illite

IlliteThe Illite clays have a structure similar to thatof muscovite, but is typically deficient inalkalies, with less Al substitution for Si.  Thus,the general formula for the illites is:

KyAl4(Si8-y,Aly)O20(OH)4 , usually with  1 < y< 1.5, but always with y < 2.

Because of possible charge imbalance, Ca andMg can also sometimes substitute for K.

The K, Ca, or Mg interlayer cations prevent theentrance of H2O into the structure.  Thus, theillite clays are non-expanding clays.  

Illite type clays are formedfrom weathering of K and Al-rich rocks under high pHconditions. Thus, they form byalteration of minerals likemuscovite and feldspar. Illiteclays are the main constituentof shales.

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Montmorillonite

Montmorillonite or smectiteis family of expansible 2:1phyllosilicate clays havingpermanent layer chargebecause of the isomorphoussubstitution in either theoctahedral sheet (typicallyfrom the substitution of lowcharge species such as Mg2+

, Fe2+, or Mn2+ for Al3+)

Montmorillonite

The most common smectite is Montmorillinite, with a general chemical formula :

(1⁄2Ca,Na)(Al,Mg,Fe)4(Si,Al)8O20(OH)4.nH2O

Montmorillinite is the main constituent of bentonite, derived by weathering of volcanicash.  Montmorillinite can expand by several times its original volume when it comes incontact with water.  This makes it useful as a drilling mud (to keep drill holes open), and toplug leaks in soil, rocks, and dams.  

Montmorillinite, however, is a dangerous type of clay to encounter if it is found in tunnelsor road cuts. Because of its expandable nature, it can lead to serious slope or wall failures. 

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Smectite group clays

SEM View of Montmorillonite

From Yucca Mountain, NV

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Swelling ClaysThe interlayer in montmorillonite orsmectites is not only hydrated, but it isalso expansible; that is, the separationbetween individual smectite sheetsvaries with the amount of water presentin the soil. Because of this, they areoften referred to as "swelling clays".

Soils having high concentrations ofsmectites can undergo as much as a30% volume change due to wetting anddrying or these soils have a highshrink/swell potential and upon dryingwill form deep cracks.

bentonite

Clay Minerals are a product of weathering

•Reducing SiO2 and K Occurs during weathering

*These elements, along withothers, are removed by fluids(mainly water)

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Painted Desert, NM

Bentonite-bearing shales, such as in the Painted Desert, arederived from weathering of volcanic ash. The leaching of silicais responsible for preservation of petrified wood

VermiculiteVermiculite is a high-charge 2:1phyllosilicate clay mineral. It isgenerally regarded as a weatheringproduct of micas. Vermiculite isalso hydrated and somewhatexpansible though less so thansmectite because of its relativelyhigh charge.

Granular clay absorbents, such asvermiculite, have been used for over 75years to clean up minor drips, spills andover sprays in factories and garages

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Vermiculite structure

Vermiculite

Vermiculite possesses the special property ofexpanding to between six and twenty times itsoriginal volume when heated toapproximately 1,000 degrees Celsius. Thisprocess, called exfoliation, liberates boundwater from between the mica-like layers ofthe mineral and literally expands the layersapart at right angles to the cleavage plane.

Vermiculite is used to loosen and aerate soilmixes. Mixed with soil, it improves waterretention and fertilizer release, making it idealfor starting seeds. Also used as a medium forwinter storage of bulbs and flower tubers.

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Mining of Bentonite

Early Americans found bentonite vital to their lives. Pioneers found moistenedbentonite to be an ideal lubricant for squeaky wagon wheels. The mixture was alsoused as a sealant for log cabin roofing. The Indians found bentonite useful as asoap.

Clay quarry, UK

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Bentonite Mines - USADuring the Cretaceous,volcanoes in the Yellowstonearea of Wyoming were subjectto long periods of eruptions. Ashfalling from these eruptionsdropped into seas which coveredmuch of Wyoming, forming asediment as much as 50 feetdeep. These sediments wereslowly altered into the clayknown as bentonite.

In these deposits are contained70% of the world's knownsupply of western or sodiumtype bentonite.

Al, Si, OH Al, Si, K, OH

Al, Ca, Fe, Mg, Si,OH, H2O

Al, Ca, Na, Fe, Mg, K, Si,OH, H2OMain cations:

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Swelling ClayMapping - USGSSmectite group- montmorillonite

and othersRed = High swelling clay contentBlue = Next highBrown = Minimum

mud cracks of clay

Swelling Clay Mapping - USGSRed = High swelling clay contentBlue = Next highBrown = Minimum

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Uses of ClayOf course, soils…flowers don’t easily grow out of rocks!

Uses of Clay - Soils … or do our many grain foods, such as wheat

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Soil HorizonsThe perfect soil: 1/3 each of sand, silt, and clay

Spheriodal Weathering, San Diego Co.

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Corn, Cactus, andFlowers

all need proper soils

Uses of Clay - Oil & Water Drilling

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Uses of Clay - Drilling Mud

Bentonite and other clays are used in the drilling of oil and water wells.The clays are turned into mud, which seals the walls of the boreholes,lubricates the drill head and removes drill cuttings.

Drilling mud slurry

Cooling andcleaning the drill “Gushers” used to be

common until the useof drilling mud wasimplemented

deep oil is at high pressure

Drilling Fluid: Lifeblood ofthe Well

In 1900, while drilling an oil well inSpindletop, Texas, workers ran a herd ofcattle through a pit filled with water. Themud that resulted, a viscous, muddyslurry of water and clay, was pumpedinto the borehole. Drilling fluids are stillcalled mud, but engineers no longer relyonly on water and clay. Instead, theycarefully design compounds and mixturesto meet specific needs under variousdrilling conditions. Modern drilling fluidsare truly the lifeblood of the well.Today's deep wells could not existwithout them.

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Oil Wells

Baytown, TexasCentral Texas

These wells could never have been drilled withoutthe role of clays as drilling mud, now augmentedwith such compounds as barite

Uses of Clay - Contaminant RemovalClay slurrys have effectively been used to remove a range ofcomtaminants, including P and heavy metals, and overall waterclarification.

Schematic of montmorilloniteabsorbing Zn

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Uses of Clay

Environmental Sealants: Bentoniteis used to establish low permeabilityliners in landfills, sewage lagoons,water retention ponds, golf courseponds, and hazardous waste sites.

Filtering: Clays are used to decolorize, filter,and purify animal, mineral, and vegetable oilsand greases due to their high absorbingproperties.

Uses of ClayPharmaceuticals/ Cosmetics:Bentonite is used as a binder in tabletmanufacturing and in diarrhea medications.Clays are used as thickeners in a widevariety of cosmetics including facial creams,lipsticks, shampoos and calamine lotion.

Pelletizing: Bentonite is used to bind tinyparticles of iron ore, which are then formedinto pellets for use as feed material for blastfurnaces.

Paints: Finely ground clays are used in thepaint industry to disperse pigment evenlythroughout the paint. Without clays, itwould be extremely difficult to evenly mixthe paint base and color pigment.

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Other Uses of Clay

clay pipes

clay pots

marbles, ca. 1800

ceramic vase

Uses of Clay - Cat LitterHow a Simple Idea Improved the Quality

of Life for Millions

In 1947, an enterprising young man namedEdward Lowe assisted his neighbor with aproblem she was having. The woman wasusing ashes in her cat box and the cat wastracking the ashes throughout the house. Mr.Lowe suggested she try the all-naturalgranular absorbent clay that he was selling togarage and machine shop owners for use incleaning up minor oil spills and drips.

Both the owner and her pet loved theabsorbent clay granules. The rest, as they say,is history. From these modest beginnings, the$1.3 billion cat litter industry was born andpet ownership was changed forever.