Pyrite, marcasite, wolframite, arsenopyrite, molybdenite, rutile and cassiterite. Mount Pleasant, New Brunswick, Canada
125µm
Pyrite (light yellow-white, centre top left) forms small euhedral crystals within marcasite (blue-green white, higher reflectance, centre bottom right). This is typical of pyrrhotite replacement/alteration by iron disulphides. Rhombic arsenopyrite (white, high reflectance, bottom centre) is present. Prismatic wolframite (brown-grey, centre and left centre) is enclosed within a pseudomorph after pyrrhotite (left centre) but mainly occurs within the gangue (black). Rutile (light grey, centre) is rimmed by cassiterite (dark grey, lower reflectance than wolframite, centre). Curved laths of molybdenite (light to dark grey, bottom centre, centre right) show strong bireflectance and reflection pleochroism.
Polished block, plane polarized light, x 160, oil
