Diatomaceous Earth is a silica hydroxide sedimentary rock , is amorphous, (which means it does not have a definite crystalline structure and is therefore not a mineral) is a porous, earthy chalk like mineral, composed primarily of the remains of silica skeletons of diatoms. It has a hardness near 1, it will float on water, is white gray, or a off-white in color, and can contain water in the 3 to 13 percent range. The typical chemical composition of diatomaceous earth is 86% silicon, 5% sodium, 3% magnesium and 2% iron. The most common use of diatomaceous earth is as a filter medium. It has a high porosity, because it is composed of microscopically-small, tube like, hollow particles. Other industrial uses of diatomaceous earth is as a filler for paper, paints, ceramics, soap and detergents.

The specemin in the photo is from a California Diatomaceaous Earth Mine in Central California.