Zinc, Sphalerite (Zn)S

The chemical formula for Sphalerite , ZnS is made up of Zn, the chemical symbol for the element Zinc andS the chemical symbol for Sulfur. Neither element has been given a subscript (a number appearing after and partly below the line) which indicates that the atoms of these two elements are in equal balance, i.e. for every atom of Zn their is one atom of S.. Because Sphalerite is composed of a metal atom and the non metal atom Sulfur it is part of the mineral classification called Sulphides. Sphalerite often has some iron (Fe) atoms mined with the Zn and S, when this happens the color is usually darker.

Characteristics

Crystal Structure: Isometric
Ceavage: perfect in six directions forming dodecahedrons.
Fracture: conchoidal, but rarely seen because of frequent cleavage.
Tenacity: Brittle
Hardness: 3.5 - 4
Density: 4.096
Color : Color is typically black, can be brown, yellow, reddish, green, and less commonly white or colorless.
Streak: Brown to yellow
Luster: Resinous or adamantine to nearly metallic

Occurrence

Sphalerite is the most important zinc mineral and is found closely associated with Galena in the most important deposits of this mineral In some hydrothermal replacement bodies it is associated with Chalcopyrite, Pyrite, Pyrrhotite and Magnetite while Galena if usually not present. Sphalerite also occurs widely in hydrothermal veins and replacement bodies with Galena and in silver mines. One of Retread Resources' major projects in 1998 was to outline a sulfide bearing deposit of Silver, Galena (lead) and Sphalerite occurring in replacement bodies of rhodochrositic marble in the Cassiar region of northern British Columbia. Sphalerite (which is also known as Blende), is an important ore of zinc and can make a rather attractive cabinet specimen as well. It can have excellent luster and associates with many beautifully colored minerals making it one of the best enhancers of many fine mineral specimens. Sphalerite is one of the very few minerals that has a total of six directions of cleavage. If all of them were to be perfectly cleaved on a single crystal it would form a rhombic dodecahedron. Identifying all six directions in a single cleaved crystal is quite difficult due to the multiple twinning and the many directions. Only the fact that there is abundant cleavage at different directions can easily be seen in most cleaved specimens.

Sphalerite can be difficult to identify because of its variable luster, color, abundant but obscured cleavage and crystal habits. So difficult was sphalerite for miners to distinguish from more valuable minerals such as galena, acanthite and tetrahedrite, that they named it sphalerite which is Greek for treacherous rock and blende is German for blind or deceiving.

Sphalerite is a polymorph with two minerals, wurtzite and matraite. The three are called polymorphs (meaning many shapes) because although they have the same chemistry, (Zn, Fe)S or zinc iron sulfide, they have different structures and therefore different shapes. Sphalerite is by far the more common mineral of the three.

Sphalerite's structure is analogous to the diamond structure. If every other carbon in the diamond structure is replaced by a sulfur atom and the remaining carbons are replaced with either a zinc or an iron atom then basically the mineral is sphalerite.

Sphalerite is by no doubt the most important ore of zinc, an industrially and at times strategically important metal. Other zinc ores include hemimorphite, smithsonite, willemite, franklinite and zincite. Although its importance as an ore of zinc is undisputed, it is a very attractive and a very interesting mineral for collectors as well.

Production and use Sphalerite is the most common zinc ore mineral but not the only one. Zinc is mined in many countries around the world. Canada is the world's largest producer followed by Australia, China, Peru and the United States. These Countries accounted for 63% to total world production of zinc concentrates. The Current Average Price (October 1999) for refined Zinc is about US $ 1000/tonne (metric ton) 1998 world production was about 7.33 million tonnes. Zinc is one of the metals that is both widely used and commonly recycled.

For more information about the mineral Sphalerite , the element Zinc , or other earth science topics go to our links page or try some of these:

United States Geological Survey (USGS)
Minerals by Name
Minerals Yearbook
Amethyst Galleries' Mineral Gallery
London Metals Exchange