Diatomine or Montmorillonite ?
That is the question…
For an excellent, technical amplification of the basic information summarized in the paragraphs that follow, please refer that article:
“With or Without Salt—a Comparison of Marine and Continental-Lacustrine Diatomite Deposits” by Phillip R. Moyle and Thomas P. Dolley, [Chapter D of Contributions to Industrial-Minerals Research, James D. Bliss, Phillip R. Moyle, and Keith R. Long, Editors, Bulletin 2209–D, U.S. Department of the Interior, U.S. Geological Survey, http://pubs.usgs.gov/bul/b2209-d/b2209d.pdf [Text edited by George A. Havach, Layout by Stephen L. Scott, Manuscript approved for publication, July 24, 2003]
The name diatom comes from a Greek word diatomos that means cut in half, because the shells of diatoms have two overlapping, symmetrical halves. Diatoms are single-celled (unicellular) organisms and belong to the phylum of algae called Bacillariophyta. http://www.mii.org/Minerals/photodiatom.html They may live in colonies, or as individuals. Diatoms exist in all bodies of water upon the Earth, both salt and fresh. Diatoms form relatively hard shells made out of the silica (a gem name for of this silica is opal) that they extract from the water. As can be seen from pictures, their microscopic shells are very intricate and beautiful and have rightly been called "the jewels of the sea."
Diatoms are very abundant and provide food for many aquatic animals. There are about 60,000 species of these algae presently known. Experts estimate that there are more likely 600,000 to 6,000,000 species in total!
In North America and Europe are more than 1,000 common freshwater diatom species, with species endemic to specific ancient lakes typically ranging in abundance from 10 to 30 percent of the taxa [Moyle, et al 2003]. For an impressive list of many fresh-water species, particularly around the Great Lakes click on:
Another interesting website for tube-dwelling diatoms is : http://www.uog.edu/classes/botany/Mar_Bot/tube-dwellers.htm
An assortment of Diatomea from Ernst Haeckel's 1904 Kunstformen der Natur (Artforms of Nature)
The beautiful symmetry and design of diatoms justify their title “jewels of the sea.” Among the most important and prolific sea organisms, diatoms serve directly or indirectly as food for many animals. Diatom (dī'ətŏm', -tōm') , unicellular organism of the kingdom Protista, characterized by a silica shell of often intricate and beautiful sculpturing. http://www.answers.com/topic/diatom Their coloration is usually yellowish or brownish [(golden-brown) Barron, 1987], and besides occurring in oceans, rivers, lakes, ponds, and they may be found even in damp soil and on the moist surfaces of plants. http://en.wikipedia.org/wiki/Diatom Usual reproduction is by cell division (asexual), but under some circumstances diatoms will reproduce sexually. They occur as two morphologic types based on their symmetry, either centric (also called radial or circular) or bilaterally pennate (also called axial or elongate) [Wetherbee, 2002], and usually lack flagella; however, some posses one or two flagella, which can be similar or dissimilar. http://www.answers.com/topic/chrysophyta Most diatoms are autotrophic, but some symbiotic species (heterotrophs) may be found in particular habitats. The shell of silica enclosing living matter of each diatom is secreted by drawing silicon and oxygen from the water it inhabits. These shells are punctuated with depressions and minute pores that allow it to draw in nutrients. Diatoms are the principal player in the make-up of plankton. As such they are an extremely important food source for many tiny fish and other aquatic animals, on up to giant whalesharks and most whales.
Deposition of skeletal remains of diatoms accumulate on the floor of the body of water in which they once thrived. The earth’s rock record bears evidence of prolific activity from the thick layers of these fossilized silica shells. Such layers, or beds of diatoms may be called either diatomaceous earth, or diatomite depending upon their formation. http://www.mii.org/Minerals/photodiatom.html
Marine diatomites have been associated with upwell¬ing and other favorable environments since the time when diatomaceous silica became a significant component in Cretaceous marine sediment [Heath, 1974; Barron, 1987]. A fossil record of diatoms extends from the Cretaceous to the Holo¬cene [Boardman et al, 1987]. Other evidence in sediment as suggests the existence of marine diatoms as old as early Tertiary or Late Cretaceous (when continental diatoms apparently evolved from marine ancestors), or even Jurassic while the Miocene was a time of both marine and continental diatom productivity, rapid evolution, and environments favorable for preservation [Bradbury and Krebs 1995]. Scientists agree that our level of knowledge on this subject is still evolving.
Diatoms, both marine and non-marine, require three con¬ditions to sustain life:
1) an aqueous environment,
2) light, and
3) a continuous supply of nutrients and minerals.
While “these conditions are far from unique, satisfaction of all three condi¬tions controls sustained diatom viability and production and, thus, the distribution and size of deposits. Such nutrients as phosphates and nitrates return to the water column when the organism dies and decays on the sea floor or lake bottom. In contrast, silica incorporated into the diatom frustules is per¬manently removed from the water if it is not dissolved while passing through the water column [Harben and Kuzvart, 1996].
Therefore, a continuous supply of silica is needed to refresh the diatom-productivity zone for both marine and continental environments. Although marine environments range from the deep oceans to the continental shelf and near-shore conditions, the requirement for light and nutrients restricts viable environments to the uppermost 100 to 200 m (Barron, 1987; Boardman et al, 1987). Furthermore, most marine forms are stenosaline—that is, they tolerate only a narrow range of salinity [Sverdrup et al, 1970]”. http://pubs.usgs.gov/bul/b2209-d/b2209d.pdf
Lacustrine systems associated with volcanism that dams fluvial systems to form lakes also require continuous supply of nutrient-rich/silica-rich freshwater; however volcanic processes, such as hot springs, may provide the supply of silica needed for skeletal development [Breese, 1994].
From J & H Paleoscience we find the following definition: Lacustrine - Pertaining to, produced by, or inhabiting a lake or lakes. http://digsfossils.com/fossils/footprints_glossary.html
While temperature, salinity, pH, nutrients, and water currents vary much more widely in nonmarine than in marine environments, nonmarine diatoms are euryhaline—that is, they tolerate a wide range of salinities [Sverdrup et al, 1970] relative to the stenosaline marine diatoms described above; however, lacustrine diatoms cannot not thrive in alkaline water [Barron, 1987].
Since dilution plays such an important role in the formation of diatomite deposits, the formation of commercial quantities and grades of diatomite in marine environments is favored by a low influx of both terrigenous and biogenic sediment. When radiolarians, are associated with diatoms it is usually indicative of such biogenic dilution factors being present. Besides radiolarian, a wide range of contaminants are associated with dia¬tomaceous sediment. Chert, manganese nodules, phosphates (for example, vivianite), silicoflagellates, sponge spicules, ostracods, and bivalves, as well as volcanic rocks, are more likely associated with marine deposits [Shenk, 1991; Breese, 1994]. While diatoms in sedimentary deposits of marine and conti¬nental, especially lacustrine, origin have similar nutrient (for example, phosphate, nitrate, and silica) and light require¬ments their geologic ranges and physiographic environments vary. Inland basins are consequently not as valuable diatom reservoirs for the quarrying of diatomite because of the flashflood introduction of excess clastic sediment and volcanic ash with nowhere to run-off and that becomes cumulative. These factors contribute to the usual light color of diatomite may be shaded according to its purity.
On the other hand for the formation of clay, laden with trace elements and interbedded with organic material, these conditions are ideal, and enhance its nutritive properties. Visible stratification and discoloration in clays is often indicative of a more valuable sediment containing humic matter and other interesting minerals for agricultural purposes. In conclusion of this point, what is bad for Diatomite may be good for Montmorillonite. The same kind of organic matter that enriches the Montmorillonite clay
must be subjected to processing designed to remove it from Diatomite.
Where possible, heated air is used to dry and transport dia¬toms through the beneficiation process, including separation of diatoms from denser and coarser contaminants and classification of diatoms into different sizes. Selected grades of natural diatomite may be calcined in a kiln at 870–1,093°C, volatilizing such contaminants as organic matter, CO2, and pore water to produce a pink granular material. [Cummins, 1960]
Uplift of both lacustrine and marine deposits exposes them to weathering and erosional processes, making them accessible to modern large-scale quarry operations such as “open pit mining”. Best preserved marine depos¬its are covered by younger marine sediment in postdeposition process. Fortunately, volcanic flows covered and protected many continental lacustrine deposits, particularly in the Great Basin, Columbia River Basin, and Snake River Plain in the Western United States, adding to our resources of potential diatomite exploitation today.
Barron, J.A., 1987, Diatomite-environmental and geologic factors affecting its distribution, in Hein, J.R., ed., Siliceous sedimen¬tary rock-hosted ores and petroleum: New York, Van Nostrand Reinhold, p. 164–178.
Boardman, R.S., Cheetham, A.H., and Rowell, A.J., 1987, Fossil inver¬tebrates: Boston, Blackwell Science, 713 pages.
Bradbury, J.P., and Krebs, W.N., 1995, Fossil continental diatoms; paleolimnology, evolution, and biochronology, in Blome, C.D., Whalen, P.M., and Reed, K.M., convenors, Siliceous microfossils (Short Courses in Paleontology): Knoxville, Tenn., Paleontological Society, no. 8, p. 119–138.
Breese, O.Y., 1994, Diatomite, in Carr, D.D., ed., Industrial minerals and rocks (6th ed.): New York, American Institute of Mining, Metallurgical, and Petroleum Engineers, p. 397–412.
Cummins, A.B., 1960, Diatomite, in Gillson, J.L., ed., Industrial miner¬als and rocks (nonmetallics other that fuels) (3d ed.): New York, American Institute of Mining, Metallurgical, and Petro¬leum Engineers, p. 303–319.
Harben, P.W., and Kuzvart, Milos, 1996, Diatomite, in Industrial miner¬als—a global geology: London, Industrial Minerals Information Ltd., p. 161–167.
Heath, G.R., 1974, Dissolved silica and deep-sea sediments, in Hay, W.W., ed., Studies in paleo-oceanography: Society of Eco¬nomic Paleontologists and Mineralogists Special Publication 20, p. 77–93.
Sverdrup, H.U., Johnson, M.W., and Fleming, R.H., 1970, The oceans, their physics, chemistry, and general biology: Englewood Cliffs, N.J., Prentice-Hall, 1,087 pages.
Moyle, P.R., and Dolley, T.P., 2003, With or Without Salt—a comparison of marine and continental-lacustrine diatomite deposits: U.S. Geological Survey Bulletin 2209–D, 11 pages.
Shenk, J.D., 1991, Lacustrine diatomite, in Orris, G.J., and Bliss, J.D., Some industrial mineral deposit models; descriptive deposit models: U.S. Geological Survey Open-File Report 91–11–A, p. 23–25.
Wetherbee, Richard, 2002, The diatom glasshouse: Science, v. 298, no. 5593, p. 547.