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
Schiehallion including dog's mercury, lily of the valley and wood anemone. The majority of Schiehallion consists of Quartzite, a rock formed from an original sand by heat and pressure. Quartzite is a white or pinkish rock, in which the dominant mineral is Quartz. Quartz is hard, being number seven on the Mohs scale of mineral hardness. It is able to scratch glass since it is harder than glass. People often mistakenly think that Schiehallion is an extinct volcano because its shape is reminiscent of an active volcano. If fact it formed by sedimentary processes and the shape is the result of