Zoisite

Zoisite is a polymorph of clinozoisite. A polymorph is a mineral that has the same chemical composition of another, but has a different crystal structure.

Ca₂Al₃O(SiO₄)Si₂O₇(OH)

Clinozoisite
Properties:

• hardness-6 to 6.5
• specific gravity-3.1 to 3.4
• cleavage-perfect
• fracture-uneven
• luster-vitreous
• transparency-transparent to translucent
• color-light green to yellow or gray
• streak-white

Clinozoisite crystallizes in the monoclinic system while zoisite crystallizes in the orthorhombic system. Crystals of clinozoisite are prismatic, fibrous, or acicular with the crystal faces often showing striations. Granular, massive, and fibrous aggregates are also common. Clinozoisite is a product of metamorphism of calcium rich rocks. Without X-ray analysis it can be difficult to tell clinozoisite and zoisite apart.

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