Rubies, sapphires, emeralds and the coloured stones collectors fight over.
By Shreya S · Last reviewed 15 November 2026
What are the precious stones?
Traditionally four: diamond, ruby, sapphire and emerald. Rubies and sapphires are the same mineral, corundum. Red corundum, coloured by chromium, is ruby; every other colour is sapphire, from the classic blue to pink and the orange-pink padparadscha. Emerald is a green variety of beryl.
Where do the best ones come from?
Origin changes value. The most prized rubies come from Mogok in Myanmar, with a deep “pigeon’s blood” red. The most famous sapphires came from Kashmir, mined for only a few years in the 1880s, along with Sri Lanka and Myanmar. Colombia, especially the Muzo mines, produces the finest emeralds. Emeralds almost always contain inclusions, which the trade calls the jardin, or garden.
Is “semi-precious” still a thing?
The term is falling out of use, because some so-called semi-precious stones are rarer and more expensive than many rubies. Spinel was long mistaken for ruby (the “Black Prince’s Ruby” in the British crown is a spinel), Paraíba tourmaline glows neon blue, and tanzanite, found only in Tanzania, was named and launched by Tiffany in 1968.
Are gemstones treated?
Very often. Heating rubies and sapphires to improve colour is common and accepted; oiling emeralds to hide fissures is standard. What matters is disclosure. A lab report will say whether a stone is treated and, for important stones, give an opinion on its origin. An untreated stone of top colour can be worth many times a heated one.
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