Reflected Light
PPL: pinkish gray to pinkish light brown color. Weak violet to bluish-gray pleochroism. 26% reflectivity with light bireflectance.
XPL: strong and colorful anisotropy, from gray-green to orange-brown or dark blue to brown. Rare deep red reflections.
Images: in XPL+2º, enargite with typical anisotropy.
PPL: pale pinkish-brown, yellowish color. 29% reflectivity. Weak bireflectance and pleochroism (note twins!)
XPL: strong anisotropy between greenish yellow and purple. Oblique extinction by twin planes. It has no internal reflections.
Images: Twinned luzonite in PPL and XPL+2º (with photoshop!)
PPL: color in brown and yellow tones with pink, similar to bornite. It tarnishes very quickly to brown. Weak to absent pleochroism. Reflectivity from 37 to 42%, no bireflectance.
XPL: strong anisotropy from yellow-gray to soft green, gray to bluish. Brown color is strong, blue is more discreet. No internal reflections.
Images: Arsenopyrite (PPL = white) and pyrrhotite in PPL and XPL. The gray-brown colors of pyrrhotite are very easy to identify.
PPL: gray-brown to gray-rose color, without pleochroism. Reflectivity of 19%, with weak bireflectance (see grain limits and twins!). It is a very common opaque in many igneous and metamorphic rocks, along with magnetite.
XPL: strong anisotropy in shades of gray, one of the colors has a well-defined bluish tone (observe with CPL+2º). Very rare reflections.
Images: Ilmenite in PPL (gray-rose) and in XPL (gray-bluish).
PPL: copper red to light grayish orange color, very similar to bornite color. No pleochroism. 31.5% reflectivity, no bireflectance. It always occurs as a fine lamellar alteration product in bornite. It does not tarnishes, unlike bornite.
XPL: very strong anisotropy between blue-green (turquoise) and reddish brown. No internal reflections.
PPL: white to pinkish-brown, similar to tenorite and enargite. No pleochroism. Reflectivity 19 to 23%, with distinct bireflectance.
XPL: strong anisotropy between bluish and gray. No internal reflections. It is associated with native copper, tenorite, cuprite and goethite.
Images: in PPL and XPL, delafossite.
