Everything about Soapstone totally explained
Soapstone (also known as
steatite or
soaprock) is a
metamorphic rock, a talc-
schist. It is largely composed of the mineral
talc and is rich in
magnesium. It is produced by dynamothermal
metamorphism and
metasomatism, which occurs at the areas where
tectonic plates are
subducted, changing rocks by heat and pressure, with influx of fluids, but without melting. It has been a medium for carving for thousands of years.
Petrology
Petrologically, soapstone is composed dominantly of
talc, with varying amounts of
chlorite and
amphiboles (typically
tremolite,
anthophyllite, and
magnesiocummingtonite), and trace to minor FeCr-
oxides. It may be
schistose or massive. Soapstone is formed by the metamorphism of
ultramafic protoliths (
for example dunite or
serpentinite) and the
metasomatism of siliceous
dolostones.
Pyrophyllite, a mineral very similar to talc is sometimes called soapstone in the generic sense since its physical characteristics and industrial uses are similar, and because it's also commonly used as a carving material. However this mineral typically doesn't have such a soapy feel from which soapstone derives its name.
Physical characteristics and uses
Steatite is relatively soft (because of the high talc content, talc being one on
Mohs hardness scale), and may feel soapy when touched, hence the name. Soapstone is used for inlaid designs, sculpture,
coasters, and kitchen
countertops and sinks. Traditional
Inuit carvings often use soapstone, and some
Native American groups made bowls, cooking slabs, and other objects from soapstone, particularly during the Late
Archaic archaeological period. Soapstone is sometimes used for fireplace surrounds and woodstoves because it can absorb and evenly distribute heat while being easy to manufacture. This is found in many upscale Alaskan homes. It is also used for griddles and other cookware.
Tepe Yahya, an ancient trading city in southeastern Iran, was a centre for the production and distribution of soapstone in the 5th–3rd millennia BC
Another instance of use in the ancient world is found in
Minoan Crete at the Palace of
Knossos, where
archaeological recovery has included a magnificent
libation table made of steatite.
Soapstone has been used in
India for centuries as a soft medium for carving, but unfortunately the world wide demand for soapstone is threatening the habitat of India's tigers. The
Hoysala Empire temples were made from soapstone.
Soapstone is used by
welders and
fabricators as a marker because, due to its resistance to heat, it remains visible when heat is applied. Soapstone is used to create molds for the
casting of
pewter objects.
Soapstone
smoking pipes are found, for example, among Native American Indian artifacts.
Locally quarried soapstone was used for gravemarkers in 19th century northeast Georgia around Dahlonega and Cleveland, as simple field stone and "slot and tab" tombs.
The term steatite is sometimes used for soapstone. It may also denote also a type of
ceramic material made from soapstone with minor additives and heated to
vitrify (to change or make into
glass or a glassy substance, especially through heat fusion). It is often used as an
insulator or housing for electrical components, due to its durability and electrical characteristics and because it can be pressed into complex shapes before firing. It was used for beads and seals in ancient civilizations. Steatite undergoes transformations when heated to temperatures of 1000-1200 °C into
enstatite and
cristobalite; in the Mohs scale, this corresponds to an increase in hardness from 1 to 5.5-6.5.
Other names
Kisii stone from Kenya is a type of pyrophyllite used by the
Kisii people of the Tabaka Hills in Western Kenya. They use this material to make pots, used to carry fat for massaging into their skin to guard against the elements.
Combarbalite stone, exclusively mined in Combarbala, Chile, is known for its many colors. While they're not visible during mining, they come out after refining.
Palewa and gorara stones are types of Indian soapstone.
A variety of other regional and marketing names for soapstone are used.
Further Information
Get more info on 'Soapstone'.
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