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Chemical Components of Soapstone

Soapstone is a very common stone that is used for many purposes, but its unusual softness makes it particularly desirable for carving. It is mainly noted for this softness and the greasy, soapy feel that it is named for. The main component of soapstone is talc, but other components of soapstone include chlorite, dolomite and magnesite.

Talc
- Talc (Mg3Si4O10(OH)2) is one of the softest minerals on Earth, with a hardness of 1 on the Mohs hardness scale. It is soft enough to easily carve or crush. Talc is unusual in that it breaks apart into thin sheets and has perfect cleavage when broken. This phenomenon causes talc to have a greasy feel to it. The talc content of soapstone is so high that soapstone could be considered impure talc.
Chlorite
- Chlorite (Mg,Fe,Al)6 (Si,Al)4O10(OH)8) is a general name for several similar minerals. Together, they are referred to as the chlorite group. Like talc, chlorite has perfect cleavage in one direction and is also very soft, a 2 or 3 on the Mohs hardness scale. Chlorite is typically green in color, but can be found in other colors when other trace elements are present in the crystal. This mineral is translucent or transparent.
Dolomite
- Dolomite (CaMg(CO3)2) is a common mineral with a Mohs hardness of 3.5-4. Although dolomite comes in several colors, it is most noted for its pink color and pearly luster; in addition, dolomite has an unusual curved crystal structure. It is used to make magnesia and magnesium salts. Since it is an attractive stone, the more colorful specimens of dolomite are used for artistic or ornamental purposes, and they are valued by collectors.
Magnesite
- Magnesite (MgCO3) is part of the calcite group of minerals. It is usually white and dull in color, and has a typical Mohs hardness of 3.5-4. While magnesite can be found in several different formations, it is not usually found in well-formed crystals. Magnesite is almost identical to dolomite, with the exception that dolomite is often found in distinctive, curved crystals that magnesite does not form. This mineral is an ore of magnesium, and is also used for artistic purposes, such as making beads or sculptures.
Chemical Composition of Soapstone
- The overall chemical composition of soapstone varies, but is typically 60-62 percent silicon dioxide (SiO2), 30-33 percent magnesium oxide (MgO), 0.25-0.28 percent aluminum oxide (Al203) and less than 1 percent calcium oxide (CaO) and iron oxide (Fe203).

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