Reflected Light
PPL: white color, without pleochroism. 42% reflectivity, no bireflectance. Many polishing scratches (Mohs= 2.5). Low relief. If in large crystals, it shows triangular polishing pits. The better the polishing, the fewer polishing pits and scratches will be present.
XPL: isotropic and without internal reflections. Polishing scratches and polishing pits can simulate anisotropy.
Images: in PPL, galena with polishing pits and polishing scratches.
PPL: blue-gray or blue-white color, with very weak pleochroism. 30% reflectivity, no bireflectance. Many scratches.
XPL: Very dark, with very weak anisotropy, almost imperceptible. No reflections. It looks like an isotropic mineral! It is associated with other Cu minerals such as bornite and secondary minerals (covellite).
Images: in PPL, chalcocite (white), bornite (pink) and gangue (dark).
PPL: cream-white color, without pleochroism. 54% reflectivity, no bireflectance. Zonation is common (alternating black and white bands with defined angles between segments (zig-zag)).
XPL: isotropic and without internal reflections. Pseudo-cleavage very evident. Zonation can occur.
Images: in PPL, skutterudite (white) with zonation.
PPL: white color, somewhat cream to gray, without pleochroism. 45% reflectivity, no bireflectance. Without polishing scratches (Mohs=5.5).
XPL: isotropic and without internal reflections. Perfect cleavage {100} in 3 directions. Form cubes, long straight lines and triangular polishing pits. Zonation is common.
Images: in PPL, gersdorffite (white) with cubic cleavage, nickeline (yellow).
Extremely rare!
PPL: white color, sometimes with cream or bluish tones. Reflectivity 65%. No pleochroism. No bireflectance.
XPL: isotropic and without internal reflections. Inclusions and zoning is very common. Very common Os and Ir unmixings.
Images: in PPL, platinum (white) with iridium unmixings.
PPL: silver-white color, a little cream, without pleochroism. Reflectivity 82%, no bireflectance. Lots of polishing scratches. Extremely luminous, blinds the eyes of the observer!
XPL: isotropic, scratches simulate anisotropy. No internal reflections. Common twins. Zonation and association with acanthite (AgS) common.
Images: in PPL, silver (white) with quartz (dark gray) and nickeline (orange)
