The Probert Encyclopaedia of Rocks & Minerals

TALC

Talc has the formulae Mg3Si4O10(OH)2 and a relative hardness of 1. It is a mineral of secondary origin formed by the alteration of magnesium silicates. Usually found in metamorphic rocks where, in a non-crystalline form, it occurs as 'soapstone' - and can make up large rock masses. Used for laboratory table tops and for many industrial uses. It has a greasy feel.
Research Talc