Sphalerite

Sphalerite from the Elmwood Mine, Carthage, Tennessee, U.S.A., measuring 60 × 40 × 28 mm and weighing 90 grams. A good example of a species the Central Tennessee zinc district is particularly well regarded for.

Sphalerite is zinc sulfide, ZnS, isometric, and the Elmwood Mine's crystals are known for their resinous lustre and a colour range running from pale amber through deep reddish-brown, often showing clear growth zoning. The Central Tennessee district is a carbonate-hosted, Mississippi Valley-type zinc deposit, in which zinc-rich hydrothermal fluids moved through Ordovician limestone, precipitating Sphalerite in open vugs and solution cavities rather than as a tightly disseminated ore, which is exactly the kind of setting that produces well-formed, collector-grade crystals rather than only massive ore.

Elmwood's Sphalerite has a strong following among American mineral collectors specifically for its crystal quality rather than rarity, and a piece like this is a reliable, representative example of the locality. This piece carries a double provenance, the David Vince Collection and Willyama Minerals.