What is Soapstone?

Soapstone is a metamorphic rock that is composed primarily of talc, with varying amounts of chlorite, micas, amphiboles, carbonates and other minerals. [4] Because it is composed primarily of talc it is usually very soft. Soapstone is typically gray, bluish, green or brown in color, often variegated. Its name is derived from its soapy feel and softness.

The name soapstone is often used in other ways. Miners and drillers use the name for any soft rock that is soapy or slippery to the touch. In the craft marketplace, sculptures and ornamental objects made from soft rocks such as alabaster or serpentine are often said to be made from soapstone. Be careful when purchasing if the type of rock used in making the object is important to you.

Many people use the name steatite interchangeably with soapstone. However, some people reserve the name steatite for a fine-grained unfoliated soapstone that is nearly 100% talc and highly suited for carving.

How Does Soapstone Form?

Soapstone most often forms at convergent plate boundaries where broad areas of Earth crust are subjected to heat and directed pressure. Peridotites, dunites and serpentinites in this environment can be metamorphosed into soapstone. On a smaller scale soapstone can form where siliceous dolostones are altered by hot, chemically-active fluids in a process known as metasomatism.

Physical Properties of Soapstone

Soapstone is composed primarily of talc and shares many physical properties with that mineral. These physical properties make soapstone valuable for many different uses. These useful physical properties include:
•soft and very easy to carve
•nonporous
•nonabsorbent
•low electrical conductivity
•heat resistant
•high specific heat capacity
•resistant to acids and alkalis

Soapstone is a rock and its mineral composition can vary. Its composition depends upon the parent rock material and the temperature/pressure conditions of its metamorphic environment. As a result, the physical properties of the soapstone can vary from quarry to quarry and even within a single rock unit.

The level of metamorphism sometimes determines its grain size. Soapstone with a fine grain size works best for highly detailed carvings. The presence of minerals other than talc and the level of metamorphism can influence its hardness. Some of the harder varieties of soapstone are preferred for countertops because they are more durable than a pure talc soapstone.