Over hundreds of years, a reputation for quality and excellence has been acquired by gems from certain countries and, for example,
rubies from Burma, sapphires from Kashmir and emeralds from Colombia are considered by the ‘market’ to be the most desirable of
their kind. Despite the geological evidence that these countries can also produce stones of inferior quality and that stones of high quality and rather similar characteristics may come from East Africa (ruby), Madagascar Gemstones are rarities in the geological world and are not evenly distributed in crustal rocks.
(sapphire) and Nigeria or Pakistan (emerald), the market desire for top quality stones from the traditional countries remains undiminished. Indeed, demand has grown for certificates to state their country of origin and the attachment of one of these to a particular stone can significantly enhance its value.
Most origin certificates are issued by reputable independent gem laboratories, but some stones do not contain sufficiently distinctive
characteristics to determine where they come from, and the question of their country of origin is debatable. Such a stone may pass through less than scrupulous hands and emerge with a probable ‘origin’. This has had the effect of discouraging use of the term ‘origin’ in any objective discussion about a gem in favour of more specific terms such as geological source or geographical location.
But despite their overall scarcity certain areas do seem to be favoured with local concentrations of a number of gem species while others are barren. Among the better endowed are the very old shield areas of the major continents, and of these, Brazil, East Africa, South India and Sri Lanka are exceptional. The shield areas are also the locations for kimberlites and gem diamonds, the richest regions being southern Africa, Siberia and, more recently, north-western Canada. Other favoured localities containing gem minerals occur in major fold belts, with emeralds coming from the Andes in Colombia, the Urals in Russia and the Himalayas in Pakistan; rubies also from the Himalayas in Pakistan and Nepal and from their extension into Myanmar (formerly known as Burma); jades come from the Rockies in western Canada, the mountainous South Island of New Zealand and, again, from Myanmar. Pegmatites can provide a wide range of gem minerals including beryl, garnet, kunzite, topaz and tourmaline, and examples can be found both in shield areas such as Minas Gerais (Brazil) and in fold belts such as in California.
Large areas of New South Wales and Queensland, central Thailand and central Nigeria are covered with basaltic rocks which are associated with sapphires, zircons and spinels. Also in parts of Australia, but far removed from mountain building or volcanic action, precious opal was formed in the tranquil conditions of near-surface groundwaters. Many other gem Origins or districts could be cited, but reference is more appropriately made to them where individual gem species are described.