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
Frederic E. Mohs was largely unsuccessful, as many surgeons were not comfortable learning skin pathology and laboratory techniques. Dermatologists, who are well trained in dermatopathology, and who treat skin cancers on a daily basis, quickly embraced the procedure. Today, most Mohs procedures are performed by dermatologists, although a small number of plastic surgeons, otolaryngologists, and pathologists are also practicing and using the procedure as well. Mohs' technique was later modified by Perry Robins in the 1970s, using fresh-tissue frozen histology. Rather than using the anesthetic Mohs paste, local anesthetic is used. The fresh skin specimen is then mounted on a cryostat, and frozen