Sphalerite is a very common mineral that is a member of the sulfides. This mineral is infusible if pure, but, as the iron content of this mineral increases, it becomes more fusible. Varieties of sphalerite, which are rich in manganese, are triboluminescent. Because sphalerite is common, it is found all over the world, including the tri-state mining district in the U.S., which is composed of the following states: Missouri, Kansas and Oklahoma.
Composition
Sphalerite is a zinc iron sulfide. Its mineral crystals belong to the isometric system, typically forming in tetrahedral or pseudo-octahedral shapes. Often, these crystals form with rounded edges. Sphalerite varies in color, from yellow to reddish brown, if nearly pure. If iron is present, it can be blackish. There are also pink, green and colorless varieties. Striated faces are common.
Physical Properties
Sphalerite is a semihard mineral having a rating of 3.5 to 4 on the Mohs hardness scale. On this scale, a diamond is a 10. The mineral is heavy and yet very fragile, having perfect cleavage, which breaks away parallel to the 12 faces of the dodecahedron. The mineral is transparent or translucent with adamantine or resinous luster. It leaves a pale yellow or reddish streak. Sphalerite is soluble in hydrochloric acid and will give off hydrogen sulfide fumes.
Environment
To understand sphalerite's composition, you will need to understand the environment in which it is formed. Sphalerite predominately comes from pegmatitic-pneumatolytic veins and from hydrothermal veins associated with galena, argentite, greenockite, chalcopyrite, barite and fluorite. It can be found in sedimentary deposits, believed to be of chemical origin, and in low and high temperature replacement deposits, such as in skarns. It can also be found in metamorphic environments.
Uses of Sphalerite
The main use for sphalerite is as a source for zinc ore. As byproducts, mining sphalerite for zinc also provides cadmium, gallium and indium. Zinc is important because it is one of the components for making brass and other metal alloys. It is also used as sheet zinc and for galvanizing iron.
Tags: Composition Sphalerite, pure iron, yellow reddish