Friedrich Mohs harder. This became the basis of the hardness scale developed by Mohs. The hardest mineral, diamond was given a value of 10 and softer minerals such as talc were given the very low value of 1 (unity). Other minerals were given intermediate values, depending on their ability to scratch another mineral in the scale. Thus gypsum was given the value 2 because it will scratch talc crystals, and calcite the value 3 because it will scratch gypsum. Minerals are also now classified by chemical characteristics, but the physical properties are still useful in field examination. In 1812, Mohs became a
Bursaite hand samples of bursaite appear to be nearly identical to the mineral lillianite. In a microscope, bursauite shows distinct high reflective power and oblique extinction. The reflectance values are Rγ' = ~43 and Rα' = ~38 (in nm). The birefringence is generally weak in air, but stronger when bursaite is immersed in oils. Bursaite has a hardness of 2.5 on the Mohs scale. It has a gray, metallic luster that appears white in polished sections. The mineral is also known to have good tabular cleavage along the (100) planes. Like many sulfosalts, bursaite occurs in regions abundant in sulfur. Close