Wyoming Means Quality
clay in Wyoming
formed naturally from the chemical weathering of volcanic materials such
as tuff or glass, volcanic ash, other igneous and sedimentary rocks. First
mined and developed during the 1880's, demand and value of Wyoming bentonite
clay increased, and bentonite clay deposits were soon discovered in other
parts of Wyoming during the 1920's. The first bentonite processing plant
was built shortly after this, followed by many other competitive plants
built to process Wyoming bentonite. The largest deposits of commercial
sodium bentonite are found in Wyoming, Montana and South Dakota.
Wyoming bentonite is composed essentially of montmorillonite
clay, also known as hyrdous silicate
In laymans terms, Wyoming bentonite is formed much like a deck of cards
sandwiched together. When exposed to water, these cards or clay platelets
shift apart. Attracting water to its negative face, bentonite holds the
water in place similar to iron to a magnet. Because of this unique characteristic,
this unique material is capable of adsorbing 7 to 10 times its own weight
in water, and swelling up to 18 times its dry volume. Over the years,
the area has become famous as the location unique to this high quality
material, resulting in the states' name being synonymous with the quality.
Montmorillonite and Adsorption
has a crystalline structure. It results in a "flake" particle
shape that resembles a corn flake. These flakes are extremely small, ranging
in long dimension from 10 micrometers to 0.01 micrometers. Hundreds of
such flakes aggregate to form a thin particle. One gram of montmorillonite
has a surface area of 750 m2/gram, nearly as much as the best activated
carbon grains. Twelve grams have a surface area that covers an entire
football field. This variance in thickness is related to the adsorption
of water and other polar molecules.
The material is always electrically unbalanced by substitutions,
such as magnesium, iron, or calcium replacing aluminum. This results in
a charge deficiency that must be balanced externally by cations, which
in turn are exchangeable. The quantity of cations required to create a
net charge balance is called "the exchangeable cation capacity."
The internal charge deficiency inside it results in a net negative charge
of the particle, which in turn is compensated for by exchangeable cations
positioned but weakly held near the tetrahedral layers. The most prominent
cations are sodium, calcium, magnesium, and potassium, respectively.
The exchangeability of these cations
allows this material to remove heavy metals from water, an important consideration
for wastewater treatment. Simultaneously, it removes cationic organics
by ion exchange, resulting in an interaction with polymers. Its large
swelling capacity, combined with ion exchange capacity, allows the material
to form a floc with suspended solids that can be precipitated out of the
The combination of the relative purity, its unusual geochemistry
and structure is why the material is unique to this area of the world
is an extremely high quality material. Purity is defined by the amount
of sodium montmorillonite as compared to the other minerals present. A
typical sample contains up to 90% montmorillonite while other similar
materials produced around the world have only 70-80% montmorillonite.
The color of the material can range from white to light olive green, cream,
yellow, earthy red, brown and sometimes sky blue when fresh but yellowing
rapidly with exposure to air. When wet it is highly plastic and slippery,
often appearing greasy or waxy.