variscite

Variscite
General
Category	Phosphate mineral
Chemical formula	AlPO4·2H2O
Identification
Color	Green, blue green, yellow green and rarely red
Crystal habit	Encrustations and reniform masses
Crystal system	Orthorhombic - dipyramidal
Cleavage	[010] perfect
Fracture	Conchoidal to splintery
Mohs Scale hardness	4.5
Luster	Vitreous to waxy
Streak	White
Diaphaneity	Transparent to translucent
Specific gravity	2.57 to 2.61
Optical properties	Biaxial (-)
Refractive index	nα = 1.563 nβ = 1.588 nγ = 1.594
Birefringence	δ = 0.031
References	[1][2][3]

Cut slab of Variscite at the Smithsonian. Specimen is roughly 0.5 m wide.

Variscite is a hydrated aluminium phosphate mineral (AlPO₄·2H₂O). It is a relatively rare phosphate mineral. It is sometimes confused with turquoise; however, variscite is usually greener in color.

Variscite is a secondary mineral formed by direct deposition from phosphate-bearing water that has reacted with aluminium-rich rocks in a near-surface environment. It occurs as fine-grained masses in nodules, cavity fillings, and crusts. Variscite often contains white veins of the calcium aluminium phosphate mineral crandallite.

Variscite is sometimes used as a semi-precious stone, and is popular for carvings and ornamental use. It was first described in 1837 and named for the type locality of Variscia, the historical name of 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.^[4]

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 County.^[5]

Notable localities are Lucin, Utah and Fairfield, Utah in the United States. It is also found in Germany, Australia, Poland, Spain^[6] and Brazil.

Gem quality variscite, Nevada

References

See also

• List of minerals