(The first instalment of this article appeared in our issue of June 2-8, 2003.)
Mention “the big three,” and many people will immediately think: Roosevelt, Churchill and Stalin. Or perhaps the younger among us will imagine a burger, fries and a shake. Regardless, the big three are actually ruby, sapphire and emerald, representing the three primary colours: red, blue, and green. Next to diamonds, they are the best known, the most popular, the most widely available, and generally the most expensive of all coloured gemstones. They are also the most widely counterfeited (as discussed in Part 1), but that’s another story.
Actually, these three gemstones comprise only two minerals, as ruby and sapphire are both varieties of the mineral corundum, an alumina oxide. With a hardness of nine, corundum is very durable, has a high lustre, and under certain geological conditions will grow into transparent crystals. If contaminated by trace amounts of chromium, it will turn a beautiful, glowing, deep reddish pink, and be called a “ruby.” If contaminated by trace amounts of titanium, with a wee bit of iron, it will turn deep blue and be known as “sapphire.” Any gem variety of corundum other than ruby is known as sapphire, and any sapphire other than blue (and there are many) should be prefixed by the colour (for example, “purple sapphire,” “yellow sapphire,” etc.). Given that rubies and sapphires are rarely completely transparent, they are commonly heated, which improves their transparency while brightening their colour. Unfortunately, they are often subject to many other treatments as well, and usually these are not disclosed.
The world’s best rubies and sapphires come from a small area in Myanmar, where extra-fine cut stones more than a carat or two in size can fetch retail prices of more than US$10,000 and $5,000, respectively, per carat, even if they have been heat-treated. From anywhere else, prices are about half at the top end but closer as you move down. Rubies and sapphires are also found in Thailand, Sri Lanka, Australia, East Africa, and Montana. Most production is from placer deposits (versus lode), and most mining is carried out on a small scale by small groups of locals who use old, primitive, or manual methods to recover the stones.
However, several companies use modern, industrial methods to explore for and mine rubies and sapphires. Australian miner
Elsewhere in the world,
Gem varieties
Emerald, the green member of this primary-colour triumvirate, has a hardness of 7.5-8 on the Moh scale and is the chromium-coloured gem variety of the mineral beryl (sometimes with vanadium, too), a beryllium silicate; similar to fine ruby, top-grade emerald virtually glows. Other gem varieties of beryl include aquamarine (pale greenish-blue), heliodor (yellow), morganite (pink), goshenite (colourless), and bixbite. Bixbite is an extremely rare red variety found only in the Wah Wah mountains of Utah (Kennecott attempted to commercially mine them). Prices for extra-fine emeralds are generally between those for sapphire and ruby. Among the other beryls, only bixbite comes close in price to emeralds, the king of beryls. Similar to rubies and sapphires, natural emeralds usually contain inclusions and fractures, and as a result, they are often treated prior to being sold, usually with a liquid to fill and thus obscure the fractures (oil or polymer); once again, these treatments are not always disclosed. There are also manufacturers of synthetic emerald, just as there are of ruby and sapphire.
Emeralds have been mined since ancient times, one of the oldest sources being the area near the Red Sea in Egypt. Today, the Muzo and Chivor regions of Colombia produce the finest gems (unfortunately, a Canadian company, Chivor Emerald, attempted to develop and produce emeralds there without success). However, fine emeralds are also found in Brazil, Tanzania, Madagascar, South Africa, India, Pakistan, Russia, North Carolina, and, most recently, the Yukon.
True North Gems
Emeralds were accidentally discovered in the Yukon in 1998 by
Several Canadian companies are pursuing emeralds elsewhere in the world.
,000, which is equivalent to more than US$3,000 per carat, or more than US$15,500 per gram (compared with US$11.57 for an equivalent amount of gold).
So much for the Big Three. The next article in this series will look at some of the more exotic and less-known coloured gemstones being mined around the world. Stay tuned. Meanwhile, be sure to catch the television documentary series Stones of Fate and Fortune, which is about coloured gemstones. It is being produced by the Discovery Channel. For telecast dates, see www.discovery.ca
— Avrom Howard, M.Sc, P.Geo, FGAm is a geoscientist and certified gemologist. He may be reached at avromeric.howard@utoronto.ca
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