Fossil diatoms, in the form of diatomite have been commercially mined since the late 1800's. These organisms have been living on the earth for approximately 250 million years and are represented by tens or even hundreds of thousands of different species. Despite their long history most of the commercially viable deposits were formed during the ten to fifteen million years surrounding the Late Miocene to Early Pliocene. The unique characteristics of diatomite make it useful for a wide variety of commercial applications. The United States is a major producer of diatomite products, and is home to the largest commercially mined deposit in the world. The economic production of diatomite products can be sustained well in to the future, with world reserves that should last for the next 500 years. The mining and processing of diatomite, when properly controlled, have a very minimal impact on humans and the environment.