Diatomaceous earth is a type of powder made from the sediment of fossilized algae found in bodies of water. Because the cells of these algae were high in a compound called silica, the dried sediment produced from these fossils are also very high in silica. These deposits are found all over the world. The ancient Greeks used diatomaceous earth to make building materials, like bricks and blocks. Later on it became popular in Europe for various industrial uses.