Transmitted Light
In PPL, chlorite is colorless or pleochroic in pale green. In XPL, it shows anomalous colors in blue (berlin blue), bluish-gray, purple or brown (leather brown). Monoclinic, forms lamellae, fibers or masses. Very common as metamorphic mineral or alteration product. Extinction of 0-9º (simulates parallel extinction!), but not mottled like the micas! ES(+/-), B(+/-), but crystals usually too small to determine these characteristics.
In PPL, colorless or pleochroic in pale yellow, lime green, pale green, yellow-green and brown-green. In XPL, intense anomalous colors (very colorful) with zonation (irregular distribution). Monoclinic. High relief. Granular, columnar, acicular. Rhombic basal sections. One perfect cleavage. Extinction paralell or oblique. ES(+/-), B(-), 2V=64-90º.
In PPL, colorless. In XPL, intense and/or anomalous blue colors. Prismatic, acicular in radiated aggregates, granular with pseudohexagonal sections. Monoclinic, one perfect cleavage. Extinction paralell to cleavage or oblique of 30º. ES(+/-), B(+), 2V from 40-90º. Twins rare, zonation frequent. Epidote and pumpellyite are similar.
In PPL, colorless, rarely pink without pleochroism. The variety thulite (of Mn) shows moderate pink to yellow pleochroism. In XPL, anomalous colors (blue-gray, brown) or of lower 1st order. Orthorhombic. Short to radiated prisms with rhombic or hexagonal basal sections. One perfect cleavage. Extinction //, ES(-), B(+), with 2V 0-69º.
In PPL, colorless. In XPL, anomalous brown, gray or beige colors. Low relief. Anhedral, prismatic. Tetragonal. Perfect (001) cleavage very obvious. Parallel extinction, ES(+/-). U(+), may be anomalously biaxial. Rare mineral, usually secondary, in cavities (vesicles) of basaltic volcanic rocks.
In PPL, moderate to strong pleochroism between bluish, green, green-gray, colorless or yellow-green. In XPL, lower 1st order or anomalous colors. Monoclinic or triclinic, pseudo-hexagonal. Hourglass zoning possible. High relief, cleavage not visible. Extinction tends to oblique. ES(-), twins common, B(+/-) with 2V 36-70º.
In PPL, colorless. In XPL, 2nd order or anomalous colors (blue or brown). Tabular crystals, prismatic or radiated, in bow-tie patterns. Orthorhombic. Medium relief. Good {001} cleavage. Parallel, undulating or checkered extinction. ES(+/-), rare twins, zoning possible. B(+), 2V from 64-71°. Typical of alkalinic volcanic rocks.
In PPL, colorless. In XPL may have anomalous colors such as blue or leather brown. Trigonal, prismatic or tabular crystals, with square and elongated basal sections. Poor cleavages. Parallel extinction, rare twins and zonation. U(+/-). It forms small crystals (~plagioclases) in the matrix of silica-undersaturated volcanic rocks.
In PPL, colorless, sometimes yellowish, pale green or brownish. Uneven color distribution is common. In XPL, anomalous colors are typical (low interference colors or Berlin blue, brown, purple, etc.). Granular, anhedral or short prisms. Poor cleavage. Tetragonal. Extinction tends to parallel, ES(-). Rare twins. Usually zoned. U(-), can have 2V from 17-33º.
In PPL, weak to moderate pleochroism between colorless, yellowish, light green and blue-green. In XPL, colors between 1st and 2nd order or anomalous (indigo blue and leather brown). Zoning common. Monoclinic. Lamellar, acicular or fibrous. Medium to high relief, 2 good cleavages. ES(+/-), twins common, B(+), 2V 7º-110º. Rare mineral.
