Rock N Dirt Yard is now carrying large bags of Vermiculite to help with retaining moisture in your soil. In Central Texas, where heat is high and rain usually is scarce, vermiculite helps your plants thrive. Large bags contain 4 cubic feet and cost $35.
Essentially vermiculite is a member of the phyllosilicate group of minerals, resembling mica in appearance. It is found in various parts of the world, but currently the major mines are located in South Africa, China, Brazil, Zimbabwe, and the United States. The largest operating mines today are located in the Palabora region of North-Eastern Transvaal in South Africa, in the northwestern corners of China, and along the eastern Appalachian range in the United States (Virginia and South Carolina). The vermiculite ores from these mines are different forms of hydrated phlogopite or biotite mica which has the remarkable ability of being able to expand to many times its original volume when heated—a property known as exfoliation.
From a geological perspective, almost all of the commercial vermiculite mines operating today work in deposits which were formed in pre-Cambrian and Archean deposits (1.5-3.0 billion years old). These are quite different from the former Libby, Montana deposit which was Triassic in age (225 million years old).