Soapstone
It is produced by dynamothermal metamorphism and metasomatism, which occur in subduction zones, changing rocks by heat and pressure, with influx of fluids but without melting.
[1] Petrologically, soapstone is composed predominantly of talc, with varying amounts of chlorite and amphiboles (typically tremolite, anthophyllite, and cummingtonite, hence its obsolete name, magnesiocummingtonite), and traces of minor iron-chromium oxides.
Soapstone undergoes transformations when heated to temperatures of 1,000–1,200 °C (1,830–2,190 °F) into enstatite and cristobalite; on the Mohs scale, this corresponds to an increase in hardness to 5.5–6.5.
The Yoruba of Ife also produced a miniature soapstone obelisk with metal studs called "the staff of Oranmiyan".
Soapstone mining in Tabaka, Kenya occurs in relatively shallow and accessible quarries in the surrounding areas of Sameta, Nyabigege and Bomware.
[15] In the United States, 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.
In Canada, soapstone was quarried in the Arctic regions like the western part of the Ungava Bay and the Appalachian Mountain System from Newfoundland.
[16] The ancient trading city of Tepe Yahya in southeastern Iran was a center for the production and distribution of soapstone in the 5th to 3rd millennia BC.
Pipes and decorative carvings of local animals were made out of soapstone by Australian Aboriginal artist Erlikilyika (c. 1865 – c. 1930) in Central Australia.
Vikings hewed soapstone directly from the stone face, shaped it into cooking pots, and sold these at home and abroad.
[4] In modern times, soapstone is most commonly used for architectural applications, such as counter tops, floor tiles, showerbases, and interior surfacing.
Soapstone is sometimes used for construction of fireplace surrounds, cladding on wood-burning stoves,[26][27] and as the preferred material for woodburning masonry heaters because it can absorb, store, and evenly radiate heat due to its high density and magnesite (MgCO3) content.
Resistance to heat made steatite suitable for manufacturing gas burner tips, spark plugs, and electrical switchboards.
[28] Steatite is used primarily for its dielectric and thermally-insulating properties in applications such as tile, substrates, washers, bushings, beads, and pigments.
Some of the oldest towns, notably Congonhas, Tiradentes, and Ouro Preto, still have some of their streets paved with soapstone from colonial times.
Exposure above safe limits can lead to symptoms including coughing, shortness of breath, cyanosis, crackles, and pulmonary heart disease.
Due to the potential presence of tremolite and crystalline silica in the dust, precautions should be taken to avoid occupational diseases such as asbestosis, silicosis, mesothelioma, and lung cancer.
[34] The local names for the soapstone vary: in Vermont, "grit" is used, in Georgia "white-grinding" and "dark-grinding" varieties are distinguished, and California has "soft", "hard", and "blue" talc.
