What is "saponite"

Saponite \Sap"o*nite\, n. [Sw. saponit, fr. L. sapo, -onis, soap.] (Min.) A hydrous silicate of magnesia and alumina. It occurs in soft, soapy, amorphous masses, filling veins in serpentine and cavities in trap rock.

n. (context mineralogy English) A trioctahedral smectite mineral.

Saponite is a trioctahedral mineral of the smectite group. Its chemical formula is Ca(Mg,Fe)((Si,Al)O)(OH)·n(HO). 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.