“The microstructure of high-grade Cu-Pb-Zn-Sb ore from Colquechaca. Cross-section through an ore fragment (embedded in resin) showing extremely fine-grained aggregates of pyrite crystals (slightly anisotropic) in association with sphalerite (isotropic, partially with brown-red dispersed light internal reflections), are partially cemented and/or partially replaced by porous aggregates of bournonite crystals (olive brown grey and blue grey anisotropy, with polysynthetic parquet-shaped twinning), chalcopyrite (weak olive brown to pale blue anisotropy), minor galena (isotropic) and minor quartz (various dispersed light internal reflections). Vertically reflected, plane polarized light, digital image in air, with crossed polarizers. Please compare the corresponding photomicrographs. Vintage specimen, ex Prof. G. C. Amstutz collection, Tübingen. G. Grundmann collection and photo, homemade polished section. ”

“The microstructure of high-grade Cu-Pb-Zn-Sb ore from Colquechaca. Cross-section through an ore fragment (embedded in resin) showing extremely fine-grained aggregates of pyrite crystals (pale yellow) in association with sphalerite (medium grey), are partially cemented and/or partially replaced by porous aggregates of bournonite crystals (light greenish to bluish greys), chalcopyrite (yellow), minor galena (off white) and minor quartz (dark grey to black). Vertically reflected plane polarized light digital image in air. Please compare the corresponding photomicrographs. Vintage specimen, ex Prof. G. C. Amstutz collection, Tübingen. G. Grundmann collection and photo, homemade polished section. ”