Description
The mineral zinc blende, also called blende or sphalerite (old: sphalerite), is the most important source of zinc for mining. The mineral consists largely of ZnS, zinc sulfide, and contains approximately 67% zinc. However, the mineral can also contain large amounts of iron. Cadmium can also occur in recoverable quantities. The mineral often contains inclusions of chalcopyrite (CuFeS2). Sphalerite is frequently found as an impurity in lead ore. The mineral has a hardness of 3.5–4 and an average density of 4.05. Its low hardness makes it unsuitable for jewelry. Zinc blende has a cubic crystal system with space group F-43m. It can consist of tetrahedral or dodecahedral crystals, but it generally does not have attractive crystal shapes (anhedral). Cleavage occurs along the crystal plane [110]. Twining occurs along the axis (111). The mineral can be transparent to translucent, but also completely opaque if it contains a lot of iron. Its color is usually brown, but can vary between colorless, dark brown, gray, or black. The mineral may contain brown, light yellow, or white streaks. Zinc blende has a resinous luster. The name sphalerite comes from the Greek sphaleros, meaning "treacherous." The mineral was often mistaken for galena (lead blende), but it does not contain lead. Zinc blende forms in a wide variety of hydrothermal environments. It often occurs with pyrite and galena. The type locality of zinc blende has not been further defined, and the mineral is very common. It is considered the most important ore of zinc.
Zinc blende / Sphalerite
