Xocomecatlite

Xocomecatlite is a rare tellurate mineral with formula: Cu₃(TeO₄)(OH)₄. It is an orthorhombic mineral which occurs as aggregates or spherules of green needlelike crystals.

Xocomecatlite
Xocomecatlite (green) in quartz matrix, collected from Trixie Mine, East Tintic District, East Tintic Mountains, Utah, United States
General
Category	Tellurate mineral
Formula (repeating unit)	Cu3(TeO4)(OH)4
IMA symbol	Xco[1]
Strunz classification	7.BB.50
Crystal system	Orthorhombic Unknown space group
Unit cell	a = 12.14 Å, b = 14.31 Å c = 11.66 Å; Z = 12
Identification
Formula mass	450.26 g/mol
Color	Green, emerald green
Crystal habit	Aggregates of radial to spherulitic or botryoidal acicular crystals
Tenacity	Brittle
Mohs scale hardness	4
Streak	light green
Diaphaneity	Translucent
Specific gravity	4.65
Density	4.42 g/cm3
Optical properties	Biaxial (-)
Refractive index	nα = 1.775 nβ = 1.900 nγ = 1.920
Birefringence	δ = 0.145
Pleochroism	Rich bluish greens
2V angle	Measured: 41°
References	[2][3][4]

It was first described in 1975 for an occurrence in the Oriental mine near Moctezuma, Sonora, Mexico. It has also been reported from the Centennial Eureka mine in the Tintic District, Juab County, Utah and the Emerald mine of the Tombstone District, Cochise County, Arizona in the United States. The name is derived from xocomecatl, the Nahuatl word for "bunches of grapes", and alludes to the mineral's appearance as a set of green spherules. It occurs in the oxidized zone of gold-tellurium veins in altered rhyolite. It occurs associated with other rare tellurate minerals: parakhinite, dugganite, tlapallite, mcalpineite, leisingite, jensenite; the sulfate - phosphate minerals: hinsdalite–svanbergite; and the oxide goethite.[3][4]