A very soft rock composed primarily of hydrated magnesium silicate. It is easily cut and has been used for carvings since ancient times. It is usually a white, grayish green, brown or in rare cases, red or black. The stones were carved for bowls, boxes, and small objects such as figurines, beads, seals, amulets, and scarabs. In modern construction, it is used for laboratory sinks, bench tops, and electrical panels. Native soapstone is so soft it can be scratched with a fingernail, but baking results in dehydration and hardening of the stone. Some ancient soapstone carvings were glazed then fired, which produced the mineral enstatite, hard enough to scratch glass.

Source: AAT

http://vocab.getty.edu/page/aat/300011665