Saponite

Saponite is a trioctahedral mineral of the smectite group. Its chemical formula is Ca_0.25(Mg,Fe)₃((Si,Al)₄O₁₀)(OH)₂·n(H₂O). It is soluble in sulfuric acid. It was first described in 1840 by Svanberg. Varieties of saponite are griffithite, bowlingite and sobotkite.

It is soft, massive, and plastic, and exists in veins and cavities in serpentinite and basalt. The name is derived from the Greek sapo, soap. Other names include bowlingite; mountain soap; piotine; soapstone.

Occurrence

Saponite was first described in 1840 for an occurrence in Lizard Point, Landewednack, Cornwall, England. It occurs in hydrothermal veins, in basalt vesicles, skarns, amphibolite and serpentinite. Associated minerals include celadonite, chlorite, native copper, epidote, orthoclase, dolomite, calcite and quartz.

Saponite is found in Ząbkowice Śląskie in Silesia, Svärdsjö in Dalarna, Sweden and in Cornwall, UK. The soap stone of Cornwall is used in the porcelain factory. Saponite is also found in the "dark rims" of chondrules in carbonaceous chondrites and seen as a sign of aqueous alteration.