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
Mineral Revolution and formed the basis of the apartheid system, which dominated South African society for a century. The Mineral Revolution began with the discovery of diamonds at the town of Kimberley in 1867. The discovery of diamonds led to a rush of prospectors descending on the town, whose population skyrocketed as increasing numbers of prospectors arrived to seek their fortune. As more diggers arrived in Kimberley, diamond-mining increased in scale, focusing in open-pit mining of three main sites. As surface deposits of diamonds were excavated, deeper pits had to be dug, propelling the Mineral Revolution into a new phase. To excavate