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"Ceylon sapphire" is trade shorthand for corundum mined in Sri Lanka, and the island has been digging it out of river gravel for longer than any other source still working.

Tanzanite comes from one hillside.

Colombia is the reference origin for emerald, and has been since Spanish colonial exports first reached Europe in the sixteenth century.

Thailand is where much of the world's ruby and sapphire is heated, cut and traded, whatever ground it came from.

Brazil is the most varied gem producer on earth.

Myanmar, still called Burma across the gem trade, is the origin every ruby is measured against.

Australia defined the world opal trade for more than a century and remains its reference origin, and its sapphire fields in Queensland and New South Wales supply the market with dependable dark blues, parti colours and the teal that designers cannot get enough of.

Kenya holds a singular place in the coloured stone trade as the home of tsavorite, the green grossular garnet that Campbell Bridges first found in 1967 and traced across the border to the Taita hills in 1971, and that Tiffany named in 1974 for the Tsavo national park next door.

Madagascar produces a wider spread of gem material than almost anywhere else.

Zambia is the second force in world emerald and, by volume of fine material, arguably the first.

Ethiopia became a major gem origin within living memory.

Montana is the gem origin of the United States that matters to the coloured stone trade, on the strength of one species: sapphire.

Most of the ruby sold anywhere today came out of the ground in northern Mozambique.

Vietnam entered the first rank of gem origins with the discovery of spinel and ruby around Luc Yen in Yen Bai province in the late 1980s.

Afghanistan sells four quite different things to the gem trade, and the paperwork on all four tends to be written somewhere else.

Cambodia holds two distinct places in the gem trade.

India is the source of the most valuable sapphire in the world.

Pakistan's northern mountains produce ruby, emerald, spinel, peridot, aquamarine and topaz.