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Formula: ZnS
Sulphide, wurtzite group. Wurtzite, which is trigonal or
hexagonal, is the high temperature
polytype of
sphalerite, which is isometric; the transition for
pure ZnS occurs at 1020oC, and this transition temperature is lowered by the presence of iron in solid
solution
(AM 46.1382).
Crystal System: Hexagonal
Specific gravity: 4 to 4.1 measured, 4.09 calculated
Hardness: 3½ to 4
Streak: Brown
Colour: Dark reddish-brown to black, orange-brown
Common impurities: Fe,Cd
Environments
Wurtzite is of hydrothermal origin in veins with other sulphides (Webmin, HOM), also along shrinkage fractures
in siderite concretions, of low-temperature origin. Associated
minerals include sphalerite, pyrite,
chalcopyrite, baryte and
marcasite
(HOM).
Chalcopyrite is an epitaxial mineral
(Mindat).
Localities
The type locality is the San José Mine, Oruro City, Cercado Province, Oruro, Bolivia.
At Llallagua, Rafael Bustillo, Potosí, Bolivia, wurtzite forms interlaminations in
marcasite/pyrite, and replacements of
pyrrhotite, associated with galena and
franckeite and a carbonate (siderite
or rhodochrosite). In vugs wurtzite forms crystals to 2 cm, sometimes
associated with sphalerite, wolframite
and franckeite, but most wurtzite crystals have inverted to
sphalerite. Fibrous wurtzite occurs in some veins as coatings on
sphalerite; crystals on marcasite
have been found, and also fine crystals associated with franckeite,
wavellite and vauxite
(Minrec 37.2.159-160).
Wurtzite from Llallagua - Image
At the Francon Quarry, Montreal, Quebe, Canada, a single crystal of wurtzite has been found associated with
quartz, calcite and
baryte
(Minrec 37.1.55).
Wurtzite from the Francon Quarry - Image
At the Shijiang Shan-Shalonggou mining area, Inner Mongolia, China, the mineral deposits occur predominantly in
veins of hydrothermal origin in skarn. Wurtzite occurs as 0.1 mm
dark brown crystals sometimes lodged within clusters of olshanskyite
crystals
(R&M 96.5.404).
At Johanngeorgenstadt, Erzgebirgskreis, Saxony, Germany, wurtzite was found commonly in the deposits, although in
small amounts, as gelatinous, radial or shell-like formations. It was found as red, pink and yellowish aggregates of
tiny crystalline hemispheres and as reniform coatings in the United Field mines.
(Minrec 55.5.625-626).
At Huinac, Ancash department, Peru, wurtzite is accompanied by
rhodochrosite
(Minrec 42.2.148)
At Pachapaqui, Ancash department, Peru, wurtzite is associated with quartz; there
is no evidence of rhodochrosite
(Minrec 42.2.150).
Wurtzite from Pachapaqui
At the Palitra pegmatite, Lovozero Massif, Murmansk Oblast, Russia, wurtzite occurs as crystal clusters to 1 mm on
ussingite and sodalite
Wurtzite from the Palitra pegmatite -
Image
Near Shelocta, Pennsylvania, USA, wurtzite occurs in siderite concretions. Three
new paramorphs of zinc sulfide have been described.
The zinc sulfide paramorphs occur along fractures in the concretions and
generally are embedded in
baryte. Other associated minerals include
calcite, chalcopyrite,
pyrite and sphalerite.
Sphalerite is found to have formed later than the wurtzite
(AM 35.29-42).
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