5.6" Sphalerite with Marcasite & Chalcopyrite - Missouri

This nice specimen of semi-transparent sphalerite is covered in epitactic chalcopyrite and small shards of marcasite. Around the edges of the specimen, when a light source is placed behind, a red/brown color will become apparent, likely from the iron impurities of the sphalerite mineral. Tetrahedral chalcopyrite crystals enshroud the entire specimen as well as a variety of marcasite formations scattered around the chunk of sphalerite.

Sphalerite is a part of the sulfides group and typically exhibits a grey/black appearance due to high concentrations of impurities. When sphalerite is in it's purest state, the chemical composition is ZnS, and can display a gemmy transparent light tan/yellow color. This is one of the few minerals that can form crystals ranging anywhere between gemmy and transparent to opaque and metallic-like. Opaque or cloudy sphalerite tends to be most abundant, due to the ease of iron replacing zinc in the process of formation.
Sphalerite, Marcasite and Chalcopyrite
Tri-State Lead-Zinc Mining District, Jasper County, Missouri
5.6" long, 5.0" wide, 2.4" tall