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Diatomite |
Diatomite in all of its forms, the Bentonites and the alternative Montmorillonoid classification for the broader group, aka Smectite clays, including specifically Montmorillonite, are composed largely of Silicon, once absorbed by diatoms, and originally deposited as sediment. Some species of diatoms inhabited fresh water, and some in salt water, during different periods of geologic time. [Refer to separate section on diatoms at the conclusion of this article.] The distinction between Diatomite and the Montmorillonoids is fairly simple. Diatomite is a form of silica--like a common sand by the same name. Its scientific formula is SiO2 which is also the same basic formula for chert, flint, and common quartz. However, Diatomite is usually more chalky, and often a fairly homogeneous material found in expansive deposits. Its SiO2 cousins are more rock-like, and therefore much harder--the result of an extrusive volcanic formation, causing even smaller crystal size. The diverse forms of Silicon Dioxide are a result of the impurities they contain. They are mostly found in less impressive quantities than Diatomite, and typically occur in shattered veins, as opposed to sedimentary deposits.
On the other hand, the Silicon absorbed by the species of diatoms making up Montmorillonite and the Bentonites was converted to a “silicate”, specifically an Aluminum silicate (Al SiO4)-4. As the dead diatoms settled to the lake bottom, their remains became intermixed with considerable detrital material, including other mineral particles, and organic matter. Hence, the sediment they formed became a powdery clay. Shales eventually result from and revert to clay, cyclically. As shale eventually is left exposed due to the uplifting of strata during seismic activity, eventual break-up and degradation occurs through mass wasting, weathering, and biochemical interactions, once again contributing to the formation of clay. If shale is trapped for longer periods under greater pressure, it undergoes a metamorphosis and becomes slate. Much harder than shale, slate may contain the visible petrified outlines of the remains of animals much larger than diatoms making up its basic infrastructure. But is ground up slate as effective as living clay in agricultural and nutritional applications?
Various formulae have been proposed for Bentonite, hence the term, “Bentonites.” One formula for a granular Bentonite from Wyoming is given as:
(Al, Fe1, 6 7'Mg0,33), Si4 O10 (OH) 2Na+Ca++
This particular clay is soft-gray in color, but does not necessarily represent even all of the Wyoming Bentonites, much less Bentonite, globally nor generically.
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Some producers of Bentonite package it as a product rather than sell it as an ingredient to others, hence such brand-makers can also be called “manufacturers” in that context. The labels “Sodium Bentonite” and “Calcium Bentonite” in fact, started out as marketing names for Smectite clay minerals from a particular area.
It is possible that some “manufacturers” tamper with the formulation of Bentonite by blending, or are not very explicit in stating their formulae, or perhaps are even careless in doing so, as the variety of formulae which follow, may suggest. In one case the content of Aluminum is omitted which should raise an eyebrow.
Mg5Si8O20(OH)2(OH2)4·4H2O
NaO«5 Al2«5Si3«5O10(OH)2·(H2O)
mAl2O3-nSiO2-xH2O
(Na,Ca) (Al,Mg)6(Si4O10)3(OH)6-nH20
(Na,Ca)0.33(Al,Mg)2Si4O10(OH)2·(H2O)n.[2]
How could such diverse formulations all be Bentonite? Conversely, with so many different expressions possible, how could anyone intelligently say that Bentonite and Montmorillonite were the same thing?
What may be said of Bentonite and Montmorillonite is that we seem to have a problem of semantics fed by personal connotations. If we can agree that the formula for that deposit of basic Montmorillonite, as first described in France, and later analyzed scientifically pursuant to our modern notions of chemistry and geology, can be rendered as:
Bentonite
Al2O3 – 4SiO – x H2O
2 http://en.wikipedia.org/wiki/Bentonite
