Bentonite: Uses And Sources

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Bentonite

Uses and Sources

Overview 

Made up mainly of montmorillinite, (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2·nH2O

Formed from the weathering of volcanic ash beds  Named for Fort Benton, WY, where it was first described as part of a Cretaceous tuff sequence  Grades vary, but it is generally impure, with inclusions of other smectite minerals, as well as quartz, (IMA-NA 2007) feldspar, calcite, and gypsum 

Properties & Applications  Thixotropy

– Can be semi-solid at rest, but will be liquid when agitated – Used as a thickening and suspension agent in paints, dyes, and varnishes

(KSGS 2002)

Properties & Applications  Cohesion

– Binder and pelletizer – Ironworks: ore pellets for feeding into furnaces, and as a binder in casting sand molds

(MiningLife 2005)

Properties & Applications  Absorption

/ Adsorption

– Can absorb several times it dry weight in water – Pet litter, impermeable clay liners, wastewater treatment, detergent purification, paper pulp purification, de-inking

(IMA-NA 2007)

Properties & Applications  Inertness

– Won’t kill you to eat it! – Filler in pharmaceuticals, animal feed, and cosmetics – Purifier and clarifier in beer, wine, and honey

(WSGS 2007)

Properties & Applications  Viscosity

and Plasticity

– Drilling: vertical and horizontal – Lubricates the bit, seals the walls of the borehole, removes drill cuttings – Additive in Portland cement, mortars, and specialized plasters

(WSGS 2007)

Bentonite as a Value-Added Commodity  

Bentonite is not often taken straight from the ground to market. Much purification is often undergone to specialize the product – Sieving (for granular bentonite) – Milling (fine and superfine powdered bentonite) – Removal of associated gangue minerals – Treated with acids (“bleaching earths”) – Treated with organics (“organoclays”) (IMA-NA 2007)

Bentonite Producers & Refiners      

AMCOL International (miner, refiner, large producer of bentonite products) Aqua Technologies (organoclay water treatment) Black Hills Bentonite LLC (miner and 1st-stage refiner) BPM Minerals LLC (producer) CETCO (special-purpose bentonite products) Montana Bentonite LLC (producer and refiner)

Production Methods Drilling & Sampling  Soil Profiling (to aid in speedy recovery after reclamation)  Topsoil & Overburden removal (usual with scrapers)  Quarrying with loader & truck  Only economic to mine bentonite with no more than 50 (WMA-Minelife 2007) feet of overburden 

Simplified Bentonite Mill Flow-Chart

(WMA Minelife, 2007)

World Reserves and Production Statistics Reserves of all clays used by man are extremely large, and are thought to be inexhaustible on human timescales  As a result, no concrete measurements of world reserves have been performed  It is still a very lucrative sector. US (Numbers are in thousands of metric tons) production in 2005 to 42 (USGSamounted 2007) million tons worth 

Worldwide Distribution

(Mindat 2007)

End Use Statistics

(USGS 2005)

Works Cited  

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Industrial Minerals Association of North America, www.ima-na.org, (Accessed March 23, 2007). Kansas State Geological Survey, http://vulcan.wr.usgs.gov/LivingWith/VolcanicPast/Notes/bentonite.html, (Accessed March 27, 2007). Mindat, http://www.mindat.org/min-9141.html, (Accessed March 27, 2007). MiningLife Media, http://www.mininglife.com/commodities/Bentonite.asp, (Accessed March 25, 2007). WMA-Minelife, http://www.wma-minelife.com/bent/bentmine/bentmine.htm , (Accessed March 27, 2007). Wyoming State Geological Survey, http://www.wsgs.uwyo.edu/minerals/bentonite.aspx, (Accessed March 27, 2007). USGS, http://minerals.usgs.gov/minerals/pubs/commodity/clays/, (Accessed March 27, 2007). USGS, 2005, Bentonite statistics, in Kelly, T.D., and Matos, G.R.,comps., Historical statistics for mineral and material commodities in the United States: U.S. Geological Survey Data Series 140, available online at http://pubs.usgs.gov/ds/2005/140/ . (Accessed March 27, 2007.)