On Red Variscite

by Marcus Origlieri

Lithosphere (June 1993); Fallbrook Gem and Mineral Society, Inc.; Fallbrook, CA


[Ed. Note: This article won first place in the junior article competition in both the California Federation of Mineralogical Societies and the American Federation of Mineralogical Societies in 1993.]


Variscite is a rather uncommon mineral known since 1837, when Breithaupt described material from Voigtland in Germany. The mineral name alludes to Variscia, the ancient name for the Voigtland.

Chemically, variscite is a hydrated aluminum phosphate. The pure compound is white and transparent. The variscite crystal structure accommodates iron, and variscite forms a series with a hydrated iron phosphate mineral known as strengite.

Variscite is typically green. The green color of wavellite from Arkansas has been attributed to a small vanadium substitution for phosphorus. This same hypothesis may apply to variscite. Gem green variscite contains virtually no iron.

Variscite was considered very rare until large nodules of it were discovered near Fairfield, Utah in 1894. These variscite nodules provided the first widely known gem material of an attractive green color. Other occurrences were found in Utah and Nevada. Several commercial names including amatrice and utahlite were coined to promote sales of this material.

An unusual variety of variscite occurs in certain Precambrian iron ores in the Middleback Ranges, South Australia. In the Iron Monarch deposit, apatite in the hematite ores oxidized, leading to the formation of a large suite of secondary phosphates. Among these occurs variscite, which forms crystalline coatings on hematite surfaces, rarely associated with other phosphate minerals. The variscite contains approximately 10 percent iron. Amazingly the variscite from the Iron Monarch quarry is deep rose-red and transparent. It occurs in globular surface coatings consisting of small blocky crystals. The globules may reach 3 mm in diameter. Drusy coatings are also known. Because of the black matrix and the transparency of the crystals, their overall appearance is dark cherry-red. Smaller and more opaque crystals tend to be more rose-red.

Segnit and Francis (1983) conducted a qualitative analysis on the red variscite, failing to find manganese. The identity of the chromophore remains a chagrin, although the gradation to strengite in composition may represent a plausible answer.

References

Segnit, E. R. and Francis, G. L.;
"Secondary phosphate minerals from Iron Monarch, South Australia;" Australian Mineralogist; 1, no. 43, pp. 243-250; 1983.

Sinkankas, John;
Gemstones of North America; Van Nostrand Reinhold Company, Inc., Princeton, New Jersey; 1959.

Copyright © 1993 by Fallbrook Gem and Mineral Society, Inc.

The preceding article was originally published in the June 1993 issue of Lithosphere, the official bulletin of the Fallbrook [California] Gem and Mineral Society, Inc; Richard Busch (Editor).

Permission to reproduce and distribute this material, in whole or in part, for non-commercial purposes, is hereby granted provided the sense or meaning of the material is not changed and the author's notice of copyright is retained.


Last updated: 18 September 2002
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