Sphalerite is a zinc sulfide mineral. It is the primary ore of zinc and is commonly mined for its content of cadmium, indium, germanium or gallium. It is often found in replacements, fracture filings and cavity fillings in limestone. Furthermore, it is also found in hydrothermal veins, contact metamorphism deposits and in many igneous, sedimentary and metamorphic rocks.
Sphalerite is found in a variety of colors including black, red, green, white, light brown, pale yellow and colorless. Its streak (color of mineral when its powered) can be white and brown to light yellow and its luster (the way the mineral reflects light) is resinous. Sphalerite’s hardness is between 3.5 to 4 and its specific gravity is between 3.9 to 4.1 It is chemically classified as a sulfide and its crystal system is isometric. Furthermore, according to Geology.com, it is easily identifiable as a result of its six directions of cleavage and its strong sulfur odor.
In the past, sphalerite has been difficult to identify and distinguish from more valuable minerals such as acanthite, tetrahedrite and galena. As a result, it came to be known as blended, meaning “blind” or “deceiving” in German. The word sphalerite also means treacherous rock in Greek, according to Galleries.com.
Sphalerite has the same chemistry and shape as two other minerals called wurtzite and matraite. The three minerals are called polymorphs, however, of the three, sphalerite is the most common. Zinc’s many ores include hemimorphite, smithsonite, willemite, zincite, and franklinite. However, according to Galleries.com, sphalerite is by far its most important.
Sphalerite has very little industrial use except as the main ore of zinc. An ore is a metal-bearing mineral mass that can be mined for profit. Zinc is primarily used to galvanize metal such as iron and prevent corrosion, according to
WebElements.com. It is also used for roof cladding and dry batteries. Some zinc metal is also used in lightweight coins such as the one cent found in America and Canada. The uses of zinc sulfide include the making of luminous dials, TV screens, non-toxic paints, X-ray screens and fluorescent lights.
Though the uses of sphalerite in industry are rather limited, it is highly valued in the gem and jewelery business. In pure form, sphalerite is a mineral with amazing sparkle. Its high refractive index of 2.37-2.42 is important to gemologists who take advantage by polishing the mineral and making it into a beautiful specimen.