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
Ikranite Ikranite Ikranite is a member of the eudialyte group, named after the Shubinov Institute of Crystallography of the Russian Academy of Sciences. It is a cyclosilicate mineral that shows trigonal symmetry with the space group "R"3"m", and is often seen with a pseudo-hexagonal habit. Ikranite appears as translucent and ranges in color from yellow to a brownish yellow. This mineral ranks a 5 on Mohs Scale of Hardness, though it is considered brittle, exhibiting conchoidal fracture when broken. The eudialyte group currently consists of 27 known minerals (see below), all considered rare, with the exception of eudialyte. The list below