Sfalerit

Sfalerit, known in English as sphalerite, is a zinc sulfide mineral with the chemical formula ZnS. It is the principal ore of zinc and occurs in a variety of geological settings. Sphalerite forms in two crystallographic forms: the cubic polymorph sphalerite (zinc blende), which is the common natural form, and the hexagonal wurtzite form, which is rare in nature. The mineral is isometric and often crystallizes as well-formed cubes and other cubic forms, sometimes in complex aggregates.

Physically, sfalerit has a resinous to adamantine luster and a wide color range, including colorless, yellow, brown, red, green, and black, depending on iron content and impurities. The streak is typically white to light yellow. It has a Mohs hardness of 3.5–4 and a relatively high specific gravity around 3.9–4.1. Cleavage and fracture properties vary, but the mineral is commonly described as having variable cleavage related to its crystal form and impurities.

Occurrence and formation: sphalerite is most commonly found in hydrothermal vein deposits and replacement veins, often with galena, pyrite, chalcopyrite, fluorite, and quartz. It also occurs in sedimentary exhalative deposits and some metamorphic rocks. It is widely distributed worldwide, with major producing regions in countries such as China, Canada, Mexico, Peru, Australia, and the United States.

Economic significance: sfalerit is the chief ore of zinc, frequently occurring with iron contents that influence color and other properties. Impurities can include cadmium and iron, giving rise to ferro-sphalerite varieties.