Epidote

Chemistry: Calcium aluminum silicate
Crystal system: Monoclinic; prism; deep vertical striations; seldom with distinct terminations.
Color: Transparent to translucent; Epidote: yellow, green, greenish (pistachio) brown; Clinozoisite: (low iron content) light green of greenish brown; red also known; Unakite: type of granite rock, mottled green, pink and gray.
Hardness: 6 - 7
Cleavage: Perfect: basal; Fracture: splintery, conchoidal.
Specific gravity: 3.28
Refractive index: 1.736 – 1770; Biaxial positive; Clinozoisite: 1.724 – 1.7324; Unakite: 1.52 – 1.76; 0.036 (may be lower 0.010)
Luster: Vitreous to metallic.
Dispersion: Medium
Dichroism: Strong: green, brown, yellow; chrome-light green/dark green.
Occurrence: Metamorphic and igneous; Mexico, Mozambique, Norway, USA, Austria; Unakite: South Africa, USA, Zimbabwe.

Notes
Closely related to zoisite; epidote group: zoisite and clinozoisite, epidote, piedmonite, hancockite, thulite (pink zoisite); unakite: ornamental rock containing quartz, pink feldspar and green epidote; intense band at 455nm or none depending on direction; also spectral band at 475nm; difficult to cut, faceted; unakite: beads and carvings.