Mineral necessarily constant for all sides, which is a function of its structure; crystallographic weakness renders some directions softer than others. An example of this property exists in kyanite, which has a Mohs hardness of 5½ parallel to [001] but 7 parallel to [100]. The most common scale of measurement is the ordinal Mohs hardness scale. Defined by ten indicators, a mineral with a higher index scratches those below it. The scale ranges from talc, a phyllosilicate, to diamond, a carbon polymorph that is the hardest natural material. The scale is provided below: Lustre indicates how light reflects from the mineral's
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