ClassicGems.net

Sphalerite

Discovered in 1847; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

(Zn,Fe)S

Zinc Iron Sulfide

Molecular Weight:

96.98 gm

Composition:

Zinc

64.06 %

Zn

Iron

2.88 %

Fe

Sulfur

33.06 %

S

100.00 %

Classification

Mineral Classification:

Sulphides

Strunz 8th Ed. ID:

2/C.001-10

Nickel-Strunz 10th Ed. ID:

2.CB.05

2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
C : Metal Sulfides, M: S = 1: 1 (and similar)
B : With Zn, Fe, Cu, Ag, etc.

Related to:

Sphalerite Group. Dimorph of Wurtzite.

Members of Group:

Sphalerite Group: Browneite, Coloradoite, Hawleyite, Ishiharaite, Metacinnabar, Rudashevskyite, Sphalerite, Stilleite, Tiemannite,

Varieties:

Cadmian Sphalerite, Cleiophane, Cockade ore, Gem Blende, Honigblende, Indian Sphalerite, Kokardenerz, Marmatite, Mátraite, Mercurian Sphalerite, Przibramite (of Huot),  Schalenblende

Synonyms:

Black Blende, Black Jack, Blackjack Zinc, Blende, Brunckite, False Galena, Garnet Blende, Granat-Blende, Marasmolite, Mock Lead Ore, Pseudogalena, Ruby Blende, Ruby Zinc, Wild Lead, Zinc Blende, Zincum

Crystal Data

Crystallography:

Isometric - Hextetrahedral

Crystal Habit:

Crystals tetrahedral, dodecahedral, typically complex and distorted, curved and conical faces common, to 30 cm. Also fibrous, botryoidal, stalactitic, cleavable, coarse to fine granular, massive. Twinning: simple contact twins or complex lamellar forms.

Twinning:

Twin axis [111], twin plane {111}, simple contact twins or complex lamellar forms.

Physical Properties

Cleavage:

[110] Perfect, [110] Perfect, [110] Perfect (perfect dodecahedral)

Fracture:

Conchoidal, Uneven

Tenacity:

Brittle

Moh's Hardness:

3.5 - 4.0

Density:

3.9 - 4.2 (g/cm³)

Luminescence:

Fluorescent, yellow-orange under SW UV and LW UV; Phosphorescent; Triboluminescent

Radioactivity:

Not Radioactive

Other:

Pyroelectric

Optical Properties

Color:

Colorless, Yellow, Orange, Red, Green, Brown, Black; often zoned (highly variable)

Transparency:

Transparent to Translucent; Opaque when iron-rich

Luster:

Adamantine, Resinous

Refractive Index:

2.37 - 2.43  Isotropic

Birefringence:

0.00 (Isotropic)

Dispersion:

0.156 (extremely high)

Pleochroism:

n/a

Anisotrophism:

May show strain-induced birefringence.

Occurances

Geological Setting:

Formed under a wide range of low- to high-temperature hydrothermal conditions; in coal, limestone, and other sedimentary deposits.

Common Associations:

Galena, Chalcopyrite, Marcasite, Pyrite, Fluorite, Barite, Quartz, many other hydrothermal minerals.

Common Impurities:

Mn, Cd, Hg, In, Tl, Ga, Ge, Sb, Sn, Pb, Ag

Type Locality:

Unknown

Year Discovered:

1847 (first cited in 1546)

View mineral photos:

Sphalerite Mineral Photos and Locations

Unusual Gem Categories

Fluorescent Gems, Pyroelectric Gems, Triboluminescent Gems

More Information

Mindat.org
Webmineral.com

Sphalerite's dispersion (fire) is about four times that of a Diamond! Because of its high dispersion, adamantine luster and incredible colors, it is one of the most beautiful of all cut gems. It is available in yellows, oranges, reds, browns, greens and black. All of these colors are due to the presence of iron. Sphalerite is an important ore of zinc and is the most abundant zinc mineral. Its zinc content is more than 64%. It is a soft and brittle gem so it is not suitable for jewelry.

Some Sphalerite samples may be fluorescent, showing orange under both shortwave and longwave UV light. Sphalerite is also pyroelectric, meaning it has the ability to generate a temporary voltage when it is heated or cooled. Sphalerite is also triboluminescent. Triboluminescence is a flash of light produced when a mineral is subjected to friction, such as rubbing, scratching, impact or breakage.

An iron-rich, black variety of Sphalerite is called Marmatite after its location in Marmato, Italy. A lightly colored, usually yellowish to greenish, variety of Sphalerite is known as Cleiophane.

Sphalerite was originally called Blende in 1546 by German mineralogist and metallugist Georgius Agricola (Georg Bauer) (1494 - 1555). He is known as the "father of mineralogy". Blende is from the German word blenden, meaning to glisten due to its extremely high dispersion and adamantine luster. The name Sphalerite was given in 1847 by German mineralogist Ernst Friedrich Glocker (1793 - 1858) from the Greek word sphaleros meaning treacherous, because darker varieties were often mistaken for galena (lead sulfide) but yielded no lead when smeltered.

The most notable source for Sphalerite is the Aliva mine, Picos de Europa Mountains, Cantabria [Santander] Province, Spain, but this source is now limited. Bright, beautiful green gems have been cut from material found in Bulgaria and Colorado. There are many localities for Sphalerite so only a few localities for the finest crystallized examples will be listed here. In Germany, from Freiberg, Saxony, and Neudorf, Harz Mountains. Colorless crystals in the Lengenbach quarry, Binntal, Valais, Switzerland. At Horní Slavkov (Schlaggenwald) and Príbram, Czech Republic. From Rodna, Romania. In England, from Alston Moor, Cumbria. At Dal’negorsk, Primorskiy Kray, Russia. From Watson Lake, Yukon Territory, Canada. In the USA, in the Tri-State district of the Mississippi Valley; near Baxter Springs, Cherokee County, Kansas; Joplin, Jasper County, Missouri and Picher, Ottawa County, Oklahoma. From the Elmwood mine, near Carthage, Smith County, Tennessee; in the Eagle mine, Gilman district, Eagle County, Colorado. In Mexico, from Santa Eulalia and Naica, Chihuahua, and Cananea, Sonora. At Huaron, Casapalca, and Huancavelica, Peru.

Sphalerite gems for sale: