Many minerals form beautiful crystals, but the most valued of all are gemstones. In their uncut form, they often appear ordinary and do not stand out from other stones, but after cutting, faceting, and polishing, their full colours shine through, and their values truly come to the forefront. Out of the approximately 3,800 known minerals, fewer than 100 are classified as gemstones. This classification involves various physical properties, including hardness, luster, colour, and density. Rarity, as in many other contexts, is also a value-adding factor.