Gem Minerals
Zoisite
What it is
A calcium aluminum silicate that occurs in several forms. Tanzanite is blue zoisite colored by vanadium, found in only one place on Earth. Thulite is the pink manganese-bearing variety. Ruby-in-zoisite (anyolite) is a dramatic green-and-red combination.
How it forms
Forms in calcium-rich metamorphic rocks, particularly at the contact zones between different rock types. Tanzanite specifically formed in a narrow strip of metamorphic rock near Mount Kilimanjaro.
Ca₂Al₃(SiO₄)(Si₂O₇)O(OH)
