Protogene

Protogene (Gr., 'first-born'), a granitic rock, composed of the same ingredients as true granite, but the mica is more or less altered so as to resemble talc, for which it was formerly mistaken. It received its name because it was supposed to have been the first-formed granite. It abounds in the Alps, and is found also in Cornwall. The clay produced by its decomposition is greatly valued for the manufacture of china. Protogene is now recognised to be simply an altered granite.