Sphalerite

Sphalerite is an important source of zinc, is composed of zinc sulfide in crystalline form but often contains iron.
Around 95% of zinc is extracted from sphalerite.
It is also an important source of cadmium, gallium, germanium and iridium.
When sphalerite has a high concentration of iron, it is named marmatite, a black opaque variety of sphalerite with a grey-black metal color.
Sphalerite can vary a lot from opaque minerals to clear transparent crystals.
Is often found with galena, pyrite and other sulfates together with calcite, dolomite and fluorite.
Is is also called Zinc Blende, Black-Jack or ruby jack.
Transparent cristals are used in jewelry.
An interesting variety of Sphalerite is known as Schalenblende, having bands associated with Wurtzite and often found with pyrite and galena and forms interesting concentric forms.
Pure Sphalerite has the chemical formula ZnS and is clear, with no iron in it's composition.

In it's composition there can be found alot of iron and small quantities of magnesium, cadmium, iridium, germanium and gallium. (Zn,Fe,Mg,Mn,Cd,In, Ga)S

Sulfate
Formula: (Zn,Fe)S
Composition: 64,06% Zinc; 2,88% iron; 33,06% Sulfur
Density: 3,9-4,2; average 4,05
Crystal system: Cubic/isometric
Color: brown, yellow, red, green, black
Habit: euhedral crystals, more often tetrahedal and canlook like octahedral crystals; can form masive masses and stalactites
Cleavage: perfect
Fracture: uneven to conchoidal
Hardness: 3,5-4 Mohs
Can look metalic, sub-metalic, resin or adamantin
StreakL pure sphalerite has white streak, but with impurities will have a brown-yellow streak, the streak will always be more bright then the mineral
Can be transparent to translucent or opaque if has alot of iron
Specific gravity: 3,9-4,2
Optical proprieties: isotropic
Can be found in sedimentar limestone, hipothermal veins and mesothermal, or in basalt
Rocks: igneous, sedimentar, metamorphic

Special characteristics:
Fluorescent
Triboluminoscent

Tests
Hardness: 3,5-4 Mohs
Streak white if is pure (transparent), brown-yellow if has iron and other impurities
Can have fluorescence
Often has triboluminocence
Some varieties which are transparent or translucent can have orange fluorescence in short wave UV
Dissolves in hydrochloric acid producing an sulfuric odor like rotten eggs

Varieties:
Cleiphane - transparent, bright color, a variety of sphalerite
Marmatite - opaque, metallic look, contains a lot of iron, a variety of sphalerite
Ruby jack - a red variety of sphalerite which is transparent to translcent
Schalenblende - a band form of sphalerite and Wortzite, often asociated with galena and sometimes with pyrite, the term Schalenblende is occasionally used incorrect as synonym for Wurtzite.

Asociated minerals: Galena, Fluorite, Dolomite, Quartz, Calcite, chalcopyrite, pyrite, barite

Distinguish it from other similar minerals:
Galena - more heavy (7,4-7,6), has a gray streak and a blue-metallic color
Siderite - misses brown streak, has different crystals and cleavage
Tetrahedrite - as a white-gray streak
Argentite - has a shiny-black streak and is malleable


Luminoscence :
Fluorescence: in general orange in long and short wave UV
Other colors:  yellow pale, yellow,  yellow-green, white-yellow, red-orange
Triboluminoscence - orange
Thermoluminoscence - orange
Studies shows it's emits infrared light when fluorescence

Common Activator: Mn
Other activators:Cu
Mn replacing Zn: 595 nm
V, Cl: 450-460-470nm
Cu Ga, Cu In replacing Zn: 640-670-675nm

Other sources:
http://webmineral.com/data/Sphalerite.shtml#.XaCjA0YzZrQ
https://www.minerals.net/mineral/sphalerite.aspx
http://www.fluomin.org/uk/fiche.php?id=243&name=SPHALERITE

Sources:
https://www.minerals.net/mineral/sphalerite.aspx
https://www.mindat.org/min-3727.html
http://webmineral.com/data/Sphalerite.shtml#.XaiOaOgzbvM
http://www.fluomin.org/uk/fiche.php?id=243&name=SPHALERITE

Other names: Black Jack , Belnde , Zinc Blende ,  Sphalerite , Sfalerit , sfalerite , sfaleritul , marmatite