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Chemical composition -- A family of closely related complex minerals. The best known and most valuable member of the family is a variety of zoisite better known as tanzanite, which makes gorgeous blue to purplish gems.

Color -- Colorless, shades of yellow, green, brown, black, pink.

Optics -- R.I. 1.67-1.83, depending on composition.

Durability -- Hardness 6-7. Brittle, with one direction of perfect cleavage.

Crystal structure -- Mostly monoclinic, except zoisite (tanzanite), which is orthorhombic.

Specific Gravity -- 3.1-4.2, depending on composition.

Sources -- Many widely scattered locations. Tanzanite, found only in Tanzania, is the only member of the epidote group that occurs in large facetable crystals. Facetable green epidote is usually under 5 carats. Massive unakite, a granite containing green epidote and pink feldspar, occurs as large blocks suitable for producing ornamental objects and is found throughout the Blue Ridge in Virginia, North Carolina, and Georgia.

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