Gemstones are any precious or semi-precious stones, whether as mined, or cut and polished.
There are three classic requirements for a mineral to be classed as a gemstone 1 Beauty 2 Durability and 3 Rarity . Many minerals are rare and beautiful but are far too soft to survive the rigours of being used for jewellery, for example pink calcite cuts into a spectacular stone but with a hardness of 3 on the Mohs’ scale and having perfect cleavage in several directions it is almost impossible to set the stone without shattering it let alone subject it to normal wearing comditions. Other minerals are rare and hard but just plain ugly when cut. The number of minerals that combine all three of the requirements is therefor limited.
The terms “gem” and “gemstone” mean any mineral or organic materia used for personal adornment, display, or object of art because it possesses beauty, rarity, and durability.
Of the 2,700 mineral species, only about 100 possess all these attributes. Silicates compose the largest group of gemstones; oxides and quartz compose the second largest.
