Intoxicating Beauty
An amethyst geode makes a grand entrance, and a roomful of rocks comes to life.
The world contains 3,600 mineral species--unique chemical compounds arranged just-so atomically--some of them known only in single specimens. A few of these minerals ravish the eye. Amethyst, premier purple gemstone, goes further, according to legend, and protects its possessor from drunkenness, except for that caused by beauty.
The amethyst geode shown at right--a yard across, weighing 1,600 pounds, packed with crystals of gemstone quality--is a spectacular example of a common type of amethyst specimen; Carl Francis, associate curator of Harvard's Mineralogical Museum, at 26 Oxford Street, has never seen a better one. Acquired for its crowd-pleasing properties rather than its scientific interest, it is the newly installed focal point of the museum's main exhibition hall, where 4,000 of the collection's 55,000 cataloged specimens invite examination. Both halves of the geode are on display. Francis and colleagues are in the midst of a thorough rehabilitation of the exhibits--adding interpretive guides, improving lighting, painting display cases, and bringing from storage some eye-popping gemstones--the better to discharge their curatorial responsibilities to a public ready to be seduced into learning about minerals. Harvard's systematic collection, with more than 2,000 species, is one of the world's finest and has strong seductive powers. Friends of the museum will celebrate the revivified gallery at a party in October.
The geode came out of the ground recently from a shallow mine in Amatista do Sul, Rio Grande do Sul, Brazil. It is the product of an ancient gas bubble trapped in basalt as magma cooled. An eruption of amethyst crystals, anchored in white agate, formed on the walls of the cavity, and a thin, green coating of a mineral in the mica family encased the geode, letting it later "pop right out" of the encompassing basalt, Francis explains.
Nowadays, the hard, durable, abundant birthstone of those born in February is nicely affordable, says Francis, but until the discovery at the turn of the century of rich mines in Brazil and adjacent Uruguay, amethysts came from the Ural Mountains, and "you had to be Catherine the Great to own one."
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