Sphalerite oval pendant sterling silver

Hand polished sphalerite sterling silver oval bezel necklace.
13mm x 11mm

Sphalerite is zinc sulfide (ZnS) found throughout the world. In the 1800s it was known as "blende", or "zinc blende." In its pure form, sphalerite is colorless. However, this is extremely rare in nature. Gem quality sphalerite exhibits green or orange hues that can be cut with brilliant dispersion.

Sphalerite crystals from Illinois feature zinc atoms that have been heavily replaced by Fe and other elements which lends to its resinous brown or black appearance. It is not well known in the gemological world and polished cabochons can be easily mistaken as hematite.

This particular example I collected from a Paleozoic near-surface carbonate-hosted Mississippi Valley-type (MVT) ore deposit in northern Illinois. I can supply an XRF analysis of its composition, if you're into that sort of thing.