Collecting Guide

Precious Stones & Pearls

Emeralds  |  Rubies  |  Sapphires  |  Pearls

An Emerald & Diamond suite, by Harry Winston
Sold for CHF3,044,000 ($2,465,640)
November 2006, Christie’s Geneva


Since at least 2000 B.C., long before the reign of Cleopatra, the early Egyptians were extracting emeralds from what would later by called "Cleopatra's mines", the legendary mines located between the Nile and the Red Sea. These mines were marginalised by the arrival of fine quality emeralds from Colombia in the 16th century. The mines at Chivor and Muzo have produced most of the finest emeralds ever since.

There are also important emerald deposits in Siberia, Central Africa and Brazil. Since antiquity it has been the custom to soak emeralds in colourless oils to replace the air in surface fissures thereby reducing their visibility. In recent years, other resins have been used to colour emeralds and this should be stated if good quality stones are sold.

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An oval-cut Burmese ruby ring of 7.04 carats
Sold for HK$23,060,000 ($2,970,128),
or $421,893 per carat
November 2010, Christie’s Hong Kong


Rubies are amongst the most coveted of coloured gemstones and are often associated with passion, warmth and devotion. Corundum is the name given to ruby and sapphire, although ruby is coloured by chromium and blue sapphire by a combination of iron and titanium.

The ruby's rich colour, often described as 'pigeon's blood' red, is so coveted. Clarity is also an essential ingredient of beauty and sometimes there are fine needles within the stone that reflect the light and give it a hazy shimmer at the surface.

The traditional sources for rubies are Burma (now Myanmar), Ceylon (Sri Lanka) and Siam (Thailand). The Mogok mining region of Upper Burma is synonymous with the very finest gems. Vietnam and East Africa also produce fine stones.

Rubies are often heated to improve their colour and clarity. Sometimes colourless glass-like substances are used to fill surface reaching cracks. This information should always be disclosed for major stones.

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A cushion-cut Burmese sapphire brooch of 130.50 carats
Sold for CHF6,259,000 ($7,122,742) or $55,000 per carat
World record price for a sapphire at auction
May 2011, Christie’s Geneva


Sapphires are more widely found than rubies and are often larger clearer crystals. The very finest specimens come from Kashmir, where the first discoveries were made in 1881 due to a landslide near a remote village at an altitude of over 5000 metres. The mines were depleted by 1925.

Burmese stones can sometimes rival their Kashmiri counterparts, but their colour is generally a stronger, more forceful hue than found in stones from Kashmir.

Sri Lanka has remained a key source of sapphires for more than 2000 years. Their sapphires show lighter and more delicate blues.

A wide range of colours exist for sapphires such as yellow, green, purple or the most popular of all, pink.

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The Baroda Pearls A two-strand natural pearl necklace with ear pendants, brooch & ring en suite
Sold for $7,096,000
World record price for a natural pearl jewel at auction
April 2007, Christie’s New York


Most gems are crystalline minerals produced from within the earth's surface but there are a small number that come from animals or plants. They are known as 'organic' gems.

Pearls are the most important of these materials and are found in sea-water oysters or freshwater mussels.

If a grain of sand or another irritant gets caught within the shell it is surrounded with a secretion of mother-of-pearl known as nacre.

The Persian Gulf has been the main source of fine pearls from antiquity until the 1920s. As many as 500 boats once took thousands of workers to the vast oyster beds, where the shells were resourced by hand from more than 20 metres. Today, production has all but disappeared due to pollution and lack of divers.

In 1922, Mikimoto launched the cultured pearl, which had a devastating effect on the price of pearls. The cultured pearl has remained popular ever since.

These cultured pearls are produced by inserting a round shell bead, often 7 or 8 millimetre in diameter, and thereby speeding up the natural process.

Production of white cultured pearls mainly takes place in Western Australia, Indonesia and the Philippines. Black or dark pearls, often called 'Tahitian' pearls, come from the Pacific Islands, particularly French Polynesia.

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