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TITLE: Spectacular Gems

[Photo: Various Cut Tourmalines]
The name tourmaline comes from the Sinhalese word turmali, used by Sri Lankan merchants to describe an undetermined mix of gemstones. In fact, tourmalines are a family of 11 minerals with the same basic ring-shaped arrangements of silicon, boron, and oxygen atoms. Commonly found in pegmatites, they produce some spectacular crystals and gems.

Most topaz forms in pegmatites. There it can grow into some of the world's largest gem-quality crystals, such as the two specimens 31.8 kg (70lb) and 50.4 kg (111 lb) shown here along with the 22,892,5 carat (10.10lb) American Golden Topaz gemstone. Topaz crystals generally grow from silica- and aluminum-rich solutions containing fluorine.

  [Photo: Three Large Topaz Crystals Near a Small Child]

Spodumene is found almost exclusively in pegmatites, where it can form enormous crystals — up to 14.6-m (48-ft) long! Manganese colors the pink gem variety, kunzite.

  [Photo: Spodumene ad Perl Necklace]

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Smithsonian National Museum of Natural History Department of Mineral Sciences website Credits