Talc is a mineral that is most often found in the metamorphic rocks of convergent plate boundaries. It forms from at least two processes. Most large talc deposits in the United States formed when heated waters, carrying dissolved magnesium and silica, reacted with dolomitic marbles. A second process of talc formation occurred when heat and chemically active fluids altered rocks such as dunite and serpentinite into talc.

Most of the talc deposits in the United States are in metamorphic rocks on the eastern side of the Appalachian Mountains and in rocks metamorphosed in convergent terranes of Washington, Idaho, Montana, California, Nevada, and New Mexico. Deposits of talc are also found in Texas.