Five metals-type silver association
Chloanthite (cream-white, pitted, right) has slightly lower reflectance than rammelsbergite (centre left), which shows faint reflection pleochroism from pink-white to cream-white. Rammelsbergite is overgrown by euhedral rhombs of safflorite (light blue-white, top centre left, centre left, next to pyrargyrite). Sector-twinned argentopyrite (centre) shows reflection pleochroism from light to dark brown and is intergrown with blue pyrargyrite (centre). Argentopyrite is extensively altered (left) to a mixture of pyrite, marcasite and an unnamed mineral of composition AgFe8S11 which cannot be distinguished from each other at this magnification; they are themselves intergrown with acanthite (blue-grey, lower reflectance than pyrargyrite, left centre).
Polished block. plane polarized light, x 180, oil
Argentopyrite (brown, top) shows faint reflection pleochroism from light to darker brown and is associated with pyrargyrite (blue, centre left) and an aggregate of violarite (pink-white, high reflectance, centre top) crystals. Locally, argentopyrite is extensively altered to pyrite, marcasite and AgFe8S11,, aggregates (centre right, bottom left). A veinlet of rammelsbergite (pink-white to blue-white, bottom left) shows high reflectance and faint reflection pleochroism; it is overgrown by rhombic safflorite (indistinguishable from rammelsbergite in plane polars at this magnification). The gangue is carbonate (light grey, bottom left) and quartz (darker grey, bottom centre).
Polished block. plane polarized light, x 80, air
This is the same field of view as 37b but with partially crossed polars. The anisotropy of argentopyrite (red, grey and orange, centre bottom) shows that much of it has sector twins (top centre). Rammelsbergite is also anisotropic (pink and purple) and shows polysynthetic twinning (bottom centre). Rhombic safflorite overgrowths show light blue and orange anisotropy colours (bottom centre). Pyrargyrite shows both anisotropy colours (light to dark blue, right centre) and strong red internal reflections which mask its anisotropy colours (centre top).
Polished block. partially crossed polars, x 80, air
Chalcopyrite (yellow) shows faint reflectance differences (bottom right) due to compositional variations. It encloses small pyrite crystals (light yellow, high reflectance, top right). Argentopyrite (brown) shows bireflectance and reflection pleochroism (light to dark brown) and is sector-twinned (centre left). Coarse-grained pyrargyrite (blue, centre left) is intergrown with argentopyrite. Minor amounts of fine-grained acanthite (blue-grey, bottom centre) are intergrown around argentopyrite in the calcite (grey) gangue. Carbon coating (top left) is light green-grey. Black areas are polishing pits.
Polished block. plane polarized light, x 80, air
Euhedral argentopyrite (brown) shows faint sector twinning (top centre) and reflection pleochroism (light to darker brown). Much argentopyrite has altered to a porous aggregate of pyrite and marcasite (light yellow-white, high reflectance, bottom left) which cannot be distinguished at this magnification. The iron sulphides are cemented by acanthite (blue grey, bottom left). Coarse-grained acanthite (blue-grey, soft, right) surrounds argentopyrite and encloses a euhedral crystal of pyrite (high reflectance, top right). Pyrargyrite (blue, centre left) is better polished and has a stronger surface colour than acanthite. Quartz (dark grey, bottom right) and a trigonal carbonate (dark grey, slightly higher reflectance than quartz, bottom centre) are the main gangue minerals. Black areas are polishing pits.
Polished block. plane polarized light, x160, air
Argentopyrite (brown, centre, top right) has extensively altered to a fine-grained porous aggregate of pyrite and marcasite (light yellow-white, high reflectance, bottom left) cemented by acanthite (blue-grey, top right). Euhedral unaltered argentopyrite crystals within pyrargyrite (blue, centre) are surrounded by light-sensitive rims which have etched to purple-red coloured pits (centre). With time, under strong illumination, these rims are completely destroyed. Quartz and carbonate are black with internal reflections.
Polished block. plane polarized light, x160, oil after 20 seconds