augelite
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(′öj·ə′līt)
(mineralogy) Natural, basic aluminum phosphate.
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Al
Monoclinic -- prismatic
Environment
Hydrothermal deposits; a late mineral.
Crystal descriptionMicroscopic tabular crystals in most occurrences; in one occurrence transparent and colorless, up to an inch (2.5 cm) across, and about equidimensional.
Physical propertiesColorless to white, yellowish, or rose. Luster glassy; hardness 4Ɖ-5; specific gravity 2.7; fracture conchoidal; cleavage 2 good. Brittle; transparent to translucent.
CompositionBasic aluminum phosphate (51.0% Al 2 O 3 , 35.5% P 2 O 5 , 13.5% H 2 O).
TestsSwells and whitens, retaining angular shape under blowpipe. Cobalt nitrate drop added to mass gives good blue color on second firing. Can be dissolved in acid after sodium carbonate fusion, to give chemical phosphorus test.
Distinguishing characteristicsIt would be difficult for the amateur to recognize the small crystals, since any colorless substance resembles many minerals; tests above are significant.
OccurrenceOriginally described from a Swedish occurrence where it forms no crystals. Later it was recognized as a scattering of small crystals on ore minerals in tin mines at Oruro and near Potosí, Bolivia. Became interesting when found as large (over 1 in.; 2.5 cm), well-formed, transparent, gemmy crystals at White Mountain, California, associated with other phosphates in a metamorphic andalusite deposit, and in New Hampshire pegmatites at North Groton and Newport (G.E. Smith Mine, Chandler's Mill). Most recently in Canada in the Yukon Territory (Rapid Creek) with lazulite and other phosphates.
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McGraw-Hill Science & Technology Dictionary
McGraw-Hill Dictionary of Scientific and Technical Terms. Copyright © 2003, 1994, 1989, 1984, 1978, 1976, 1974 by McGraw-Hill Companies, Inc. All rights reserved.
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