a specimen of sphalerite from from Hydraulic Shaft, Smallcleugh Mine, Nenthead, Cumbria
Also sometimes called zincblende or blackjack.
|Origin||Hydraulic Shaft, Smallcleugh Mine, Nenthead, Cumbria|
Sphalerite is a zinc sulfide mineral with a chemical composition of (Zn,Fe)S. It is found in metamorphic, igneous, and sedimentary rocks in many parts of the world. It is the most commonly encountered zinc mineral and the world’s most important ore of zinc.
Sphalerite derives its name from the Greek sphaleros (`deceitful’, `uncertain’). This is because it occurs in such varied colours that even expert miners often failed to recognise it. Even in the 16th century they still mistook it for silver ore; only in the first half of the 18th century was it discovered that sphalerite contains a significant amount of zinc. ft was, however, not used for practical purposes till the 1860s, when a metallurgical method for extracting zinc from it was worked out. Until then it had been thrown away as useless gangue, especially as it was considered an unwelcome impurity in lead ores which caused difficulties in their metallurgical processing. It is usually granular; on crevices it forms crystals of perfect cleavage and of strong metallic lustre. ft is one of the most common sulphides and occurs in ore veins, usually with galena and pyrite, and sometimes chalcopyrite (polymetallic ores). The largest sphalerite deposits are in the regions of the upper Mississippi in the USA, and in Europe on the border of Germany and Belgium. Other important deposits are at Bleiberg in Carinthia (Austria), Pribram (Czech Republic) and Bytom in Polish Silesia. Magnificent specimens of yellow crystals have been found in north-western Spain in the Picos de Europa. That particular sphalerite is ground as a precious stone. Sphalerite is the main ore of zinc, which is used mainly for metal sheets and coatings resistant to oxidation. Gallium, indium and germanium, having semiconductor properties, are present as impurities in sphalerite and are recovered from it.