Variscite Rough from Utah
Variscite is a relatively rare phosphate mineral and high quality specimens are used as gemstones and for carvings. Its name derives from Variscia, the historical name of Vogtland in Germany, where it was first found in 1837. At one time it also went under the name Utahlite, since important deposits have also been found in Utah, USA.
Variscite is often confused with turquoise, though variscite tends to be more green in color rather than blue. The variscite from Nevada, USA, which usually contains black spiderwebbing in the matrix, can easily be confused with greenish turquoise. Gemologists can definitively separate variscite from turquoise, since turquoise contains traces of copper whereas variscite does not. Variscite is colored by traces of chromium rather than copper.
By chemical composition, variscite is hydrated aluminum phosphate. It has a hardness rating of 4.5 on the Mohs scale, and is thus slightly softer than turquoise (which has a rating of 5-6). Variscite has a density of 2.42 to 2.58 and a refractive index of 1.563 to 1.594. It is typically translucent to opaque with a vitreous to waxy luster. Finished variscite will tend to display a better polish than turquoise. Variscite colors range from light bluish green, to medium and dark green and, very occasionally, red.
Variscite occurs as a groundwater precipitate in aluminum-rich rocks. It is found associated with other phosphate minerals such as apatite, wavellite and crandallite. It is rarely found in crystals and is most often found in fine-grained massive form or as encrustations in nodules, stalactites, crusts and veinlets.
The most notable variscite deposits are in Utah and Nevada in the USA. It is also found in Queensland in Australia, Germany, Poland, Spain and Brazil.