Talc Talc Talc or talcum is a clay mineral composed of hydrated magnesium silicate with the chemical formula HMg(SiO) or MgSiO(OH). In loose form, it is (in ratio with or without corn starch) one of the most widely used substances known as baby powder. It occurs as foliated to fibrous masses, and in an exceptionally rare crystal form. It has a perfect basal cleavage, and the folia are not elastic, although slightly flexible. The Mohs scale of mineral hardness, based on scratch hardness comparison, defines value 1 as the hardness of talc. Talc can easily be scratched by a fingernail. Talc
Faustite Faustite The IMA approved mineral faustite, named after the American mineralogist and petrologist with the U.S. Geological Survey (USGS) Dr. George Tobias Faust, is a member of the triclinic turquoise group of hydrous phosphates with the following chemical composition: ZnAl(PO)(OH)·4HO Some divalent copper generally replaces the zinc position. Faustite is the zinc rich analogue of turquoise having almost four times as much zinc than copper in its crystal structure. Trivalent (ferric) iron may replace some of the aluminum. Minor amounts of calcium may also be present. It has a hardness of 4.5 - 5.5 on the Mohs scale of mineral