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Dennis Kunkel's Microscopic World 2001 Calendar

Diatoms are microscopic, unicellular algae that produce intricate silica (glass) cell walls that overlap like the top and bottom of a box. When diatoms die, their soft, internal parts deteriorate, leaving their hard, porous, glass skeletons behind. Diatoms are found in aquatic environments, and saltwater diatom skeletons appear in the fossil record as early as the Jurassic period (180 million years ago). In the United States, numerous deposits of diatom skeletons are found on the floors of former aquatic inland and coastal habitats. Important commercially, diatomite is used in a variety of ways: as fine abrasive (in silver polish and toothpaste), as filters, as mineral fillers, as insulating materials, and as anti-caking agents.