Stützite

Stützite
Stützite from the Moctezuma Mine, Sonora, Mexico (size:3.7 x 3.3 x 1.7 cm)
General
Category	Telluride mineral
Formula	Ag5−xTe3 (with x = 0.24 to 0.36)
IMA symbol	Stz
Strunz classification	2.BA.30e
Crystal system	Hexagonal
Crystal class	Dihexagonal dipyramidal (6/mmm) H-M symbol: (6/m 2/m 2/m)
Space group	P6/mmm
Unit cell	a = 13.38, c = 8.45 [Å]; Z = 7
Identification
Color	Dark lead-gray
Crystal habit	Massive, compact, granular
Cleavage	None observed
Fracture	Subconchoidal
Tenacity	Brittle
Mohs scale hardness	3.5
Luster	Metallic
Diaphaneity	Opaque
Specific gravity	8.0
Alters to	Tarnishes rapidly to a dark bronze to iridescence
Other characteristics	Anisotrpism in polished section: Moderate, in gray reddish brown-blue
References

Stützite or stuetzite is a silver telluride mineral with formula: Ag_5−xTe₃ (with x = 0.24 to 0.36) or Ag₇Te₄.

It was first described in 1951 from a museum specimen from Sacarimb, Romania. It was named for Austrian mineralogist Andreas Xaverius Stütz (1747–1806).

It occurs with other sulfide and telluride minerals in hydrothermal ore occurrences. Associated minerals include sylvanite, hessite, altaite, petzite, empressite, native tellurium, native gold, galena, sphalerite, colusite, tennantite and pyrite.