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Orthoclase (Feldspar Family)

The name orthoclase is from the Greek for "straight fracture," because its two cleavage planes are at right angles to each other. Orthoclase belongs to the feldspar family of minerals that make up more than half of the Earth's rocky crust. Occasionally these common minerals form crystals that are gem quality. Orthoclase can be found as a transparent colorless, champagne, or yellow gem resembling citrine quartz or yellow beryl. This 250-carat gem is unusual because orthoclase rarely occurs in a colorful transparent form. It is rare because of its size, transparency, and vibrant yellow color. This orthoclase is from Madagascar, the most important source for gem-quality orthoclase.

Image Number: 95-40497
Catalog Number: G3878
Weight: 250 carats
Exchange, M. L. Ehrmann , 1963
Locality: Itrongahy , Madagascar

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