Transmitted Light
Strong pleochroism in green, yellow-green to bluish-green. Common amphibole. Monoclinic, 2 cleavages at 56º-124º in the basal sections (pseudo-hexagonal, rhombic). Long to short prismatic, medium-high relief. In CPL, 1st to end 2nd order colors, oblique extinction (14-22º), ES(+), twins and zoning are common, B(-).
Strong pleochroism in green (or brown or red-brown or yellow or red). Very common mica. Monoclinic. Medium relief. One perfect cleavage if not altered. Basal sections without cleavage. In CPL, 3rd-4th order colors, masked by the strong mineral color. Parallel and mottled extinction. ES(+), B(-).
Strong pleochroism between deep green, grass green and yellow-brown. Rare pyroxene. Monoclinic, high relief. Short columnar to acicular crystals. In CPL, intense 3rd and 4th order colors. 0-10º extinction, ES(-), zoning and twins are common. B(+/-). Typical of alkaline igneous rocks. Its deep colors mask the interference colors. Both images in PPL, showing typical pleochroism colors.
Strong pleochroism in green (may be in many different colors like yellow, blue, red, black and brown). Trigonal. High relief, cleavage not visible, fractures perpendicular to elongation. Basal sections (without pleochroism!) triangular or pseudo-hexagonal. Paralell extinction, ES(-), frequent zonation. U(-), can have 2V of 5º. Images of a longitudinal and a basal section.
Deep colors with pleochroism in brownish-green, blue-gray to brownish-green. It may look like an opaque mineral! Rare amphibole. Monoclinic, 2 cleavages at 56º/124º in the basal sections. Various habits. In CPL, colors are almost the same. 5-9º extinction, ES(-), twins and zoning possible, B(+/-).
Strong pleochroism between blue-green, dark blue, yellow-green and black. Rare amphibole with typical cleavage, medium to high relief, Monoclinic. Prismatic, acicular and fibrous habit. In CPL, colors up to end 1st order. Extinction 0-30º, ES (-), B(+/-). Glaucophane and tourmaline may be similar.
Weak to moderate pleochroism between colorless, yellowish, light green and blue-green. Zoning common. Monoclinic. Lamellar, acicular or fibrous. Medium-high relief, 2 good cleavages. In CPL, 1st and 2nd order colors or anomalous (indigo blue or leather brown). SE(+/-), Twins possible. B(+).
Moderate to strong pleochroism between green, green-gray, colorless, bluish, yellow-green. Monoclinic or triclinic, pseudo-hexagonal. Hourglass zoning possible. High relief, cleavage not visible. In CPL, low 1st order colors or anomalous. Extinction tends to oblique. ES(-), twins common, B(+/-). Both images in PPL.
