The genesis of gem deposits

Gem deposits are highly significant in terms of monetary value, with annual worldwide production exceeding several billion dollars. However, accurate production figures are extremely difficult to come by, as many of these deposits are worked by individuals or small groups of miners. They are of especial monetary significance in a number of developing economies in SE Asia and Africa where they account for a significant proportion of the gross domestic product, both in terms of mined rough and manufactured product. In economic geology terms, gem deposits are mostly low-tonnage and low to very low grade deposits, but of very high intrinsic value with individual gems (especially rubies and diamonds) commanding over US $5 million per carat (i.e., 0.2 g). Thus, even though some of the deposits can be of very low size, they can be more valuable than a large base metal, gold or other deposit type.