Stützite

Stützite or stuetzite is a silver telluride mineral with formula: Ag_5−xTe₃ (with x = 0.24 to 0.36)^[2] or Ag₇Te₄.^[5]

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[1]
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	[2][3][4]

It was first described in 1951 from a museum specimen from Sacarimb, Romania. It was named for Austrian mineralogist Andreas Xaverius Stütz (1747–1806).^[2][3]

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.^[2]