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
Chalcocite Chalcocite Chalcocite (), copper(I) sulfide (CuS), is an important copper ore mineral. It is opaque and dark-gray to black with a metallic luster. It has a hardness of - 3 on the Mohs scale. It is a sulfide with an orthorhombic crystal system. The term chalcocite comes from the alteration of the obsolete name "chalcosine", from the Greek "khalkos", meaning copper. It is also known as redruthite, vitreous copper and copper-glance. Chalcocite is sometimes found as a primary vein mineral in hydrothermal veins. However, most chalcocite occurs in the supergene enriched environment below the oxidation zone of copper deposits as