(WHTM) It was used in ancient times, but wasn’t “discovered” until the 1830s. It’s a mineral, but it’s produced by plants. It can be safe for humans to consume, or it can be toxic. It’s used as a filter, an abrasive, an absorbant, a paint additive, and insecticide. And it’s a byproduct of keeping our atmosphere oxygenated.

Diatomaceous earth, as the name suggests, comes from diatoms, microscopic single-celled algae. (16,000 species and counting.) They live in fresh water, salt water, and soils. As long as there’s moisture, diatoms thrive.

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They thrive by photosynthesis, a process which, among other things, takes carbon dioxide and breaks it apart, releasing oxygen. In fact, it’s estimated diatoms produce about 75% of the world’s oxygen.

Unlike other types of algae, diatoms create shells, made out of silica, or silicon dioxide. The shells are transparent; the joke that diatoms live in glass houses has a lot of truth to it.

When diatoms go off to diatom heaven, the silica shells sink to the bottom of whatever body of water they’re sinking to the bottom of. Over the years-the millions of years-these piles of shells build up into huge mineral deposits-diatomaceous earth. (If you crumble up diatomaceous earth and look at it under a microscope, you can see the shells.)

Diatomaceous earth was used in ancient times. The Chinese and Egyptians preserved food with it, and the Greeks used it for bricks and as an abrasive. But the material really attracted notice in the 1830s, when a peasant named Peter Kasten was sinking a well in Germany, and found a layer of diatomaceous earth-a layer more than 90 feet thick.

Since then deposits of the mineral have been found around the world. As more DE has become available, people have figured out more uses for it. One of its biggest uses is in filtration-everything from swimming pool and aquarium water to chemicals to pharmaceuticals to beer and wine. As an abrasive, it a shows up in metal polish, facial scrubs, and toothpaste. It’s an ingredient in paints and varnishes. It serves as a soil additive for gardening. It’s used to help clean up oil spills. In 1866, one Alfred Nobel discovered that if you mix highly unstable nitroglycerin with diatomaceous earth, it became much safer to transport. He called his invention dynamite.

Diatomaceous earth is also popular as an insecticide, killing off a lot of annoying bugs without actually poisoning them. (DE powder abosorbs lipids on bug exoskeletons which prevent dehydration; the bug then proceeds to shrivel up.)

By now you might be wondering, what about people? Is it safe for human beings to handle, or even consume, diatomaceous earth? Well, according to the Food & Drug Administration, diatomaceous earth is “Generally Recognized as Safe”. There is also “food grade” diatomaceous earth, which is purified to be low in crystalline silica, as opposed to “filter-grade” which is high in crystalline silica, and potentially toxic to humans. (When you think crystalline silica, think “microscopic shards of glass”.)

Not surprisingly, there are a plethora of websites extolling the virtues of food grade diatomaceous earth as a food additive. Not surprisingly, there are a lot of claims for diatomaceous earth that seem to have little or no scientific testing to back them up. So let the buyer beware, and be sure to do your research.