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Pallasite |
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pallasite [′palĀ·ə‚sīt]
(geology) A stony-iron meteorite composed essentially of large single glassy crystals of olivine embedded in a network of nickel-iron. An ultramafic rock, of either meteoric or terrestrial origin, which contains more than 60% iron in the former, or more iron oxides than silica in the latter. Pallasite a rare stony-iron meteorite, named after the first extant meteorite of this type, Pallas iron, discovered in Siberia by the schoolteacher Medvedev and brought to St. Petersburg on the instructions of P. S. Pallas in 1772. Pallasites are composed of approximately equal quantities of nickel iron and olivine. The unique pallasite structure indicates that these meteorites were formed during the absence of gravitational force, or at least of significant gravitational force. Want to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit the webmaster's page for free fun content. |
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