Jalpaite

Jalpaite is a rare copper silver sulfide mineral with formula Ag₃CuS₂.

Jalpaite
Jalpaite crystals from Jalpa, Municipio de Jalpa, Zacatecas, Mexico (size: 3.6 x 3.5 x 3.2 cm)
General
Category	Sulfide mineral
Formula	Ag3CuS2
IMA symbol	Jal[1]
Strunz classification	2.BA.45
Crystal system	Tetragonal
Crystal class	Ditetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m)
Space group	I41/amd
Unit cell	a = 8.67, c = 11.75 [Å]; Z = 8
Identification
Color	Pale metallic gray
Crystal habit	Irregular and foliated masses, inclusions in other minerals
Cleavage	Prismatic, good
Fracture	Subconchoidal
Tenacity	Sectile, malleable
Mohs scale hardness	2 - 2.5
Luster	Metallic
Streak	Black
Diaphaneity	Opaque
Specific gravity	6.82–6.85
Pleochroism	Distinct in oil, brownish gray to pure gray
Alters to	Tarnishes with iridescence
References	[2][3][4]

It was first described in 1858 for an occurrence in the Leonora Mine, Jalpa, Zacatecas, Mexico and named for the locality.^[3] It occurs in low temperature hydrothermal veins at temperatures less than 117 °C (243 °F). Associated minerals include acanthite, mckinstryite, galena, sphalerite, pyrite, chalcopyrite, stromeyerite, polybasite, pearceite, tetrahedrite–tennantite and native silver.^[2]