Sphalerite

• Sphalerite
• Zinc sulfide

Sphalerite, by mining also known as zinc blende or by its chemical symbol of zinc sulfide, more α - ZnS, is a commonly occurring mineral from the mineral class of " sulfides and sulfosalts ." It crystallizes in a cubic crystal system having the chemical formula of ZnS and usually develops tetrahedral and dodecahedral crystals, but also fibrous, bulky mineral aggregates in different colors ( see varieties ).

Chemically, sphalerite a salt of hydrogen sulphide and is referred to as zinc sulfide.

Sphalerite is often confused with the similar minerals magnetite and rutile. The low values ​​3.5 to 4 Mohs hardness is a reason that green colored crystals to find the sometimes found natural brown no commercial use as gemstones.

Special Features

When heated with oxygen ( roasting ) sphalerite decays as well as wurtzite to zinc oxide. This decay was formerly used among other things for the qualitative detection of zinc: on charcoal before the blowpipe is sublimed zinc oxide is deposited. This is when hot lemon yellow (see also Zinksuboxide ) and decreases only when cooled to the typical white color of the zinc oxide.

Etymology and history

The name comes from the Greek sphalerite σφαλερός sphaleros ( in German: insidious ) back because sphalerite has the specific gravity and the luster of a metal ore, but could be won until the 18th century made ​​him no metal. It was only recognized in 1735 as zinc mineral.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the sphalerite belonged to the mineral class of " sulfides and sulfosalts " and then to the Department of " sulfides with the molar ratio of metal: sulfur, selenium, tellurium = 1: 1 ," where he calls the " Sphaleritgruppe " formed as the eponymous mineral along with Coloradoite, Hawleyit, Rudashevskyit, Metacinnabarit, Polhemusit, Stilleit and Tiemannit.

The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the sphalerite also in the class of " sulfides and sulfosalts " and there in the department of "Metal Sulfides, M: S = 1: 1 ( and similar ) " a. This division, however, is further subdivided according to the dominant cation in the compound, so that the mineral according to its composition in the subsection " with zinc (Zn ), iron ( Fe), copper (Cu), silver (Ag ), etc., " Finding is where it together with Coloradoite, Hawleyit, Metacinnabarit, Polhemusit, Rudashevskyit, Sakuraiit, Stilleit and Tiemannit the " Sphaleritgruppe " with the system no. 2.CB.05 forms.

The classification of minerals according to Dana assigns the sphalerite in the class of " sulfides and sulfosalts " and there in the department of " sulfide minerals ." Here it is also named the " Sphaleritgruppe " ( Isometric: F43m ) with the system no. 02.08.02 and the other members Stilleit, Metacinnabarit, Tiemannit, Coloradoite, Hawleyit and Rudashevskyit within the subdivision " sulfides - tellurides and selenides, including - with the composition AmBnXp, with (m n): p = 1:1".

Modifications and varieties

Sphalerite is the low temperature modification of the zinc sulfide. The high-temperature modification means wurtzite or β - ZnS.

Sphalerite comes in different color and Formvarietäten ago:

• Cleiophan, green, yellow or orange
• Honey visor, clear, yellowish
• Marmatit, black by impurities of iron
• Ruby bezel, brown to red

White sphalerite is rare to find.

• Matrait, densely twinned and columnar

Education and Locations

Sphalerite forms either magmatic or hydrothermal in pegmatite. It is often associated with galena ( galena ) and other sulfide minerals, but also occurs with magnetite and pyrrhotite as ore in limestone.

Worldwide, sphalerite far (as of 2010) are detected in more than 15,000 localities, so among other things in Freiberg ( Germany ), Madan in Bulgaria, Aomori, Japan, Dzhezkazgan in Kazakhstan, Cananea in Mexico, Dalnegorsk in the Russian Federation, Trepča in Serbia, Banská Štiavnica in Slovakia, Santander in Spain, Franklin / New Jersey, Big Four Mine / Colorado, Galena / Illinois and Joplin / Missouri in the United States.

Crystal structure

Sphalerite crystallizes in the cubic crystal system in space group F43m ( Raumgruppen-Nr. 216 ) with the lattice parameters a = 5.406 Å and four formula units per unit cell.

The unit cell of sphalerite is therefore formed by two nested, face-centered cubic (fcc ) unit cell of zinc and sulfur, which are shifted by a quarter of its body diagonals against each other. " Zinc blende structure " is a fixed term for all binary crystals (such as GaAs ) with this spatial configuration. If the crystal of only one type of atom corresponds to the configuration of the diamond structure.

Use

With a zinc content of from about sixty-seven percent and relatively high cadmium content sphalerite is the main source for the industrial recovery of zinc and cadmium. Larger mining deposits are located in China, Australia and Canada.

As gem sphalerite is rarely used because it is very resistant to breakage and acid sensitive. Clear varieties of gem quality, however, may vary according to color and cut perfectly imitate more valuable gemstones such as chrysoberyl and topaz, with colorless varieties also zircon and diamond.

Another important application is together with barite, the production of white pigments based on lithopones.