Steatite

Steatite (known also by the names of soap stone and French chalk) consists of a silicate of magnesium, Mg₃Si₄O₁₂. It is a white or coloured mineral with a peculiar soapy feel, and occurs in Cornwall and in various Swedish and American localities. It is used for a variety of purposes - e.g. as a lubricant and poiishing powder, for drawing or marking on fabrics or glass, for cleaning silk, leather, etc., while its addition in the manufacture of porcelain has been found to improve the appearance of the product.