Transmitted Light
Well-defined pink color, may suggest pleochroism, but does not. Cubic. Mineral usually in rounded grains. High relief, very fractured and without cleavage. It can have many inclusions. It is ISOTROPIC; it has no interference colors, extinction, interference figure, etc. Both images in PPL.
Distinct pleochroism in pink, yellow-brown or pale green. Orthorhombic pyroxene with typical pyroxene cleavage. Usually anhedral. Basal sections may be 4- or 8-sided. Parallel extinction. In XPL, colors up to 1st order orange. ES(+), zonation common, twins rare. B(+/-), 2V = 58 to 86°. Both images in PPL, rotated 90 degrees.
Usually colorless, but may show weak pleochroism in pink. Monoclinic, lamellar. Moderate to high relief, perfect cleavage. In XPL, intense colors; parallel and mottled extinction. Twins very rare, no zonation, ES(+), B(-), 2V = 30-47º. Very common, but never occurs in volcanic rocks. Talc is very similar! Images in PPL and XPL.
The variety "fibrolite" (both images) shows a well-defined pink pleochroism. Moderate to high relief. Orthorhombic. Good cleavage // to elongation. Basal sections square/rectangular, with diagonal cleavage and gray colors. In XPL, strong colors, yellow/red/blue (0.022). Parallel extinction, ES(+). B(+), 2V from 21-30º.
Usually colorless, but may show weak pale pink pleochroism. Orthorhombic, short prisms of square section, acicular/fibrous. Perfect {110} cleavage; basal sections with 2 cleavages at 89º. Paralell extinction, symmetrical in basal sections. Black carbon inclusions are common. ES(-). B(-), high 2V. Images in PPL and XPL.
Usually pleochroic in pale blue colors, but moderate to strong pleochroism between colorless and pink may occur. Orthorhombic. High relief, prismatic habit, parallel extinction. In XPL, colors to the end of 1st order. ES(-), distinct {100} cleavage, usually occurs in Al-rich metamorphic rocks. Both images in PPL, rotated 90 degrees.
Strong pleochroism in pink (can be in red, yellow, orange or violet). Rare mineral. Monoclinic. High to extreme relief, one perfect cleavage. Long prisms, sections with 6 sides. In CPL, intense colors, masked by the color of the mineral. Extinction from 0-34º or paralell. ES(+/-), B(+/-). Both images in PPL
Usually colorless, but may show a distinct pleochroism in pink with very light yellow and violet. Orthorhombic. Rare mineral. Low relief, with 3 cleavages of good quality. In XPL, intense and colorful colors, extinction parallel to the cleavage, B(+). Usually associated with gypsum, which is gray in XPL. Images in PPL and XPL.
Strong pleochroism in sections perpendicular to (001); one of the possible colors is pale pink; sections parallel to (001) almost without pleochroism. Usually pleochroic in brown or colorless. Monoclinic. Moderate relief, one cleavage, parallel and mottled extinction, ES(+), B(-). Both images in PPL, rotated 90 degrees.
Moderate pink to yellow pleochroism in the variety thulite (of Mn). Orthorhombic. Rare mineral. High relief, short to radiated prisms with rhombic or hexagonal basal sections. One perfect cleavage. In CPL, anomalous or lower 1st order colors. Extinction paralell, ES (-), B(+) with 2V from 0 to 69º.
Rare mineral with pleochroism in rosy violet colors, may be blue. In XPL, anomalous interference colors.