Mineralogy classified into density (often given as specific gravity); measures of mechanical cohesion (hardness, tenacity, cleavage, fracture, parting); macroscopic visual properties (luster, color, streak, luminescence, diaphaneity); magnetic and electric properties; radioactivity and solubility in hydrogen chloride (). "Hardness" is determined by comparison with other minerals. In the Mohs scale, a standard set of minerals are numbered in order of increasing hardness from 1 (talc) to 10 (diamond). A harder mineral will scratch a softer, so an unknown mineral can be placed in this scale by which minerals it scratches and which scratch it. A few minerals such as calcite and kyanite
Frederic E. Mohs a boarding house. After initially considering a career as a radio engineer, he switched to medical studies in college. Mohs began developing his treatment in the 1930s, experimenting on rats, puppies, and other animals. The breakthrough came when he discovered that applying a combination zinc chloride and bloodroot paste to malignant rat skin tissue allowed it to be removed surgically and examined under a microscope. He treated his first human patient on June 23, 1936. Mohs spent his working life at the University of Wisconsin. Mohs first tried to publish his findings and encouraged surgeons to learn the procedure. This