variscite
{{short description|Hydrated aluminium phosphate}}
{{Infobox mineral
| name = Variscite
| category = Phosphate minerals
| boxwidth =
| boxbgcolor = #36c08f
| image = Variscite-Pyrite-179447.jpg
| imagesize = 260px
| caption =
| formula = AlPO4·2H2O
| IMAsymbol = Var{{cite magazine |last=Warr|first=L. N. |date=2021 |title=IMA–CNMNC approved mineral symbols |magazine=Mineralogical Magazine |volume=85 |issue=3 |pages=291–320 |publisher=Mineralogical Society of Great Britain and Ireland |doi=10.1180/mgm.2021.43 |bibcode=2021MinM...85..291W |s2cid=235729616 |doi-access=free}}
| molweight =
| strunz = 8.CD.10
| color = Pale to emerald-green (pale green in transmitted light), green, blue green, yellow green, pale shades of brown or yellow, rarely red and colourless to white
| habit = Encrustations and reniform masses
| system = Orthorhombic
| class = Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
| symmetry = Pbca
| twinning =
| cleavage = [010] perfect
| fracture = Conchoidal to splintery
| mohs = 4.5
| luster = Vitreous to waxy
| refractive = nα = 1.563 nβ = 1.588 nγ = 1.594
| opticalprop = Biaxial (−)
| birefringence = δ = 0.031
| pleochroism =
| streak = White
| gravity = 2.57 to 2.61
| density =
| melt =
| fusibility =
| diagnostic =
| solubility =
| diaphaneity = Transparent to translucent
| other =
| references ={{cite web |url=https://rruff.info/doclib/hom/variscite.pdf |title=Variscite |website=Handbook of Mineralogy |publisher=RRUFF Project}}{{Mindat |id=4156 |name=Variscite}}{{WebMineral |url=https://webmineral.com/data/Variscite.shtml |title=Variscite Mineral Data}}
}}
Variscite is a hydrated aluminium phosphate mineral ({{chem2|AlPO4*2H2O}}). It is a relatively rare phosphate mineral. It is sometimes confused with turquoise; however, variscite is usually greener in color. The green color results from the presence of small amounts of trivalent chromium ({{chem|Cr|3+}}).
Geology
Variscite is a secondary mineral formed by direct deposition from phosphate-bearing water which has reacted with aluminium-rich rocks in a near-surface environment.{{cite journal|last1=Roncal-Herrero|first1=T.|last2=Rodríguez-Blanco|first2=J. D.|last3=Benning|first3=L. G.|last4=Oelkers|first4=E. H.|title=Precipitation of Iron and Aluminum Phosphates Directly from Aqueous Solution as a Function of Temperature from 50 to 200 °C|journal=Crystal Growth & Design|date=2009|volume=9|issue=12|pages=5197–5205|doi=10.1021/cg900654m}} It occurs as fine-grained masses in nodules, cavity fillings, and crusts. Variscite often contains white veins of the calcium aluminium phosphate mineral crandallite.
It was first described in 1837 and named for the locality of Variscia, the historical name of the Vogtland, in Germany. At one time, variscite was called Utahlite. At times, materials which may be turquoise or may be variscite have been marketed as "variquoise". Appreciation of the color ranges typically found in variscite have made it a popular gem in recent years.Minerals of Nevada – Nevada Bureau of Mines Special Pub. 31 University of Nevada Press, 2004 Pages 78–81
Variscite from Nevada typically contains black spiderwebbing in the matrix and is often confused with green turquoise. Most of the Nevada variscite recovered in recent decades has come from mines located in Lander CountyGemstones of North America Volume III by John Sinkankas – Geoscience Press 1997 and Esmeralda County, specifically in the Candelaria Hills.
Notable localities are Lucin, Snowville, and Fairfield in Utah, United States. Most recently found in Wyoming as well. It is also found in Germany, Australia, Poland, Spain,{{cite web|url=http://www.patrimonigava.cat/lahistoriajaciment|title=www.patrimonigava.cat|website=www.patrimonigava.cat}} Italy (Sardinia), and Brazil.
Jewelry
Variscite has been used in Europe to make personal ornaments, especially beads, since Neolithic times. Its use continued during the Bronze Age and in Roman times although it was not until the 19th century that it was determined that all variscite used in Europe came from three sites in Spain, Gavá (Barcelona), Palazuelo de las Cuevas (Zamora), and Encinasola (Huelva).{{Cite book |last=Calvo Rebollar |first=Miguel |title=Minerales y Minas de España. Vol. VII. Fosfatos, Arseniatos y Vanadatos. |publisher=Escuela Técnica Superior de Ingenieros de Minas de Madrid. Fundación Gómez Pardo |year=2015 |location=Madrid |pages=260–276 |language=es}}
Variscite is sometimes used as a semi-precious stone, and is popular for carvings and ornamental use due to its beautiful and intense green color, and is commonly used in silversmithing in place of turquoise. Variscite is more rare and less common than turquoise, but because it is not as commonly available as turquoise or as well known to the general public, raw variscite tends to be less expensive than turquoise.{{cite web|url=https://www.gemselect.com/gem-info/variscite/variscite-info.php|title=Variscite Gemstone Information}}{{cite web|url=https://www.gemsociety.org/article/variscite-jewelry-and-gemstone-information/|title=Variscite Value, Price, and Jewelry Information – International Gem Society}}
Gallery
Variscite Smithsonian.jpg|Cut slab of variscite at the Smithsonian. Specimen is roughly 0.5 m wide.
00021 11 cm variscite.jpg|Variscite filling the cracks in siltstone. The sample is from Queensland, Australia. The width of the view is {{convert|11|cm|abbr=on}}.
Varis mcguin damali.jpg|Polished variscite from Nevada
Variscite-bolo.jpg|Variscite and silver bolo tie. This variscite specimen contains inclusions of white crandallite and is from Clay Canyon near Fairfield, Utah.
See also
- {{Annotated link|Variscan orogeny}} (same etymology, as named from the ancient locality of Variscia in Germany)
- List of minerals
References
{{commons category| Variscite}}
{{reflist}}
{{Jewellery}}
{{Phosphate minerals}}
{{Authority control}}
Category:Orthorhombic minerals
Category:Minerals in space group 61
Category:Minerals described in 1837
{{Phosphate-mineral-stub}}