Sfaleriitti

Sfaleriitti, known in English as sphalerite, is a zinc sulfide mineral with the general composition (Zn,Fe)S. Iron can substitute for zinc in its crystal structure, and small amounts of other elements may occur. Sphalerite is the principal ore of zinc, supplying most of the world’s zinc metal. It occurs in a wide range of geological environments, most notably hydrothermal veins, sedimentary exhalative deposits, and contact metamorphic zones. It commonly forms with other sulfide minerals such as galena and pyrite, and there is a ferric iron-rich variety known as ferro-sphalerite.

Crystal structure and properties: sphalerite crystallizes in the cubic system and commonly forms well-shaped crystals, including dodecahedra, as well as massive aggregates. The color range is broad, including yellow, brown, red, green, black, and colorless varieties; streak is typically pale yellow to white. It has a resinous to adamantine luster, a hardness of 3.5–4 on the Mohs scale, and a relatively high specific gravity of about 3.9–4.1. Cleavage is two directions, yielding rhombohedral fragments, and fractures are generally uneven. Sphalerite can be transparent to opaque, and many specimens fluoresce orange to yellow under ultraviolet light due to trace impurities, a feature useful for identification.

Occurrence and significance: as a major zinc ore, sphalerite has been mined worldwide. Its chemistry and the presence of iron-bearing varieties influence ore processing and smelting characteristics. The mineral is also of interest for mineral collectors due to its color variety and potential crystal shapes.

Etymology: the name derives from the Greek sphaleros, meaning deceitful, reflecting its tendency to be mistaken for other sulfide minerals.