Samples of “schalenblende” (“shell ore”) are quite striking for their brassy and silvery metallic colors mixed with brown and yellow. Schalenblende is a zinc-lead ore consisting of botryoidal crusts of brownish-colored sphalerite (zinc sulfide - (Zn,Fe)S), yellowish-colored wurtzite (zinc sulfide - (Zn,Fe)S), brassy-colored pyrite/marcasite (iron sulfide - FeS2), and silver-colored galena (lead sulfide - PbS). In the pictures of the polished specimen below, the dark gray patches are galena - they look bright silver when tilted in the light. Because of the high galena content, schalenblende samples are remarkably heavy for their size.
Locality: Pomorzany Mine, Olkúsz, Bytom (Beuthen) District, ~40 km northwest of Krakow (a.k.a. Krakau; a.k.a. Cracow), Upper Silesia, southern Poland (~50° 18’ North, ~19° 33’ East).
Origin: published research on schalenblende material indicates that mineralization was from a sulfide gel or colloidal dispersion. Crystallization took place during the early Early Cretaceous, at about 135 million years (= Valanginian Stage or Hauterivian Stage, depending on which geologic time scale one uses). This schalenblende occurrence is hosted in epigenetic dolosparites of the upper Lower Muschelkalk Formation (Middle Triassic).
Schalenblende (12.3 cm across) from the Cretaceous of Poland, with galena (silvery-black), pyrite/marcasite (grayish-gold), sphalerite (dark brown), and wurtzite (pale yellow).