Definitionn. (mineralogy) a star-shaped figure with six rays that is seen in some crystal structures under reflected or transmitted light
Last update: July 9, 2015
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Minute acicular inclusions, probably of rutile, arranged parallel to the rays of the percussion figure, give rise to the phenomenon of "asterism" in some micas, particularly phlogopite: a candle-flame or spot of light viewed through a cleavage sheet of such mica appears as a six-rayed star. [Please select]
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[Symbol: asterism] A cheaper edition, on Tinted Paper, price Half-a-Crown. [Please select]
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