SCHALENBLENDE
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).