Diamonds Are Forever

DIAMONDS ARE THE ESSENCE OF purity in Hindu myth and a girl's best friend on Broadway. That range of symbolism is one reason George Harlow, curator of gems and minerals at the American Museum of Natural History in New York, thought these precious stones deserved a show of their own. In the summer of 1995, he began organizing an exhibit called "The Nature of Diamonds." When it opens on Saturday, the display will highlight just about every facet of the hardest natural substance known to man--from the science of its origins to its beauty as a priceless gem.

Harlow calls diamonds "space capsules from deep earth." That's because each stone, whether it's the fraction of a carat in an engagement ring or the 108.93-carat Koh-i-Noor on display in the Tower of London, begins as pure carbon many miles below the surface. Heat and pressure transform it into a crystalline form. At some point, perhaps millions of years later, the crystals are thrust upward through the force of a volcano. Traces of other minerals found in diamonds give scientists using powerful electron microscopes a window into the conditions of their creation. Because of their commercial importance (diamonds are used in manufacturing and electronics), these gems have been extensively studied, and researchers have even learned how to produce artificial diamonds. The exhibit includes a re-creation of a mine and an interactive model that allows visitors to test the mineral's hardness, refraction and other properties.

One of the more surprising parts of the show is a display of more than 200 naturally colored diamonds, which have recently become more popular in jewelry. The hues are caused by the inclusion of other elements in the diamond-for example, nitrogen is primarily responsible for the intense yellow in so-called canary diamonds, while boron generally produces a blue tint.

The exhibit is not the only glittering event in New York this week. On Wednesday and Thursday, Sotheby's auctioneers will peddle what their catalog describes as "magnificent jewels," including the world's largest orange diamond, which weighs 5.54 carats and is expected to sell for more than $500,000. Not bad for a lump of coal.