Talc.
Talc is a mineral of low- to medium-grade metamorphic rocks rich in magnesium. It is often derived from ultrabasic igneous rocks made up of enstatite and olivine. It may be a major rock-forming mineral, e.g., in soapstone or steatite. It has many consumer uses, the most familiar of which is talcum powder. It has a low conductivity for heat and electricity, is fire resistant, hardens when heated to a high temperature and is not damaged by acids. It is used in ceramics, as a filler in paint, paper and rubber, and as acid-proof table-tops and sinks.

Reproduced by permission of David Liverman, Government of Newfoundland and Labrador. From Geological Survey of Newfoundland and Labrador - "Minerals of Newfoundland and Labrador: Industrial Minerals." http://www.gov.nl.ca/mines&en/geosurvey/.