How does metamorphism change talc into soapstone?
Soapstone is a form of talc. It is basically talc plus other minerals, such as micas, chlorite and amphiboles, depending on the initial rocks that were metamorphosed. Soapstone is also called a talc-schist.
Soapstone is formed by the metamorphism of ultramafic protoliths, such as dunite or serpentinite and the metasomatism of siliceous dolomites. The metamorphism occurs in the regions where tectonic plates are present, where the rocks are subjected to heat and pressure, with flowing liquids, but without melting. Soapstone is derived from hydrothemal alteration of peridotite and related ultramafic rocks.