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
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