Diatomite or Montmorillonite

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!