Question: what colors can zoisite be?
Answer: Its chemical formula is Ca2Al3(SiO4)(Si2O7)O(OH). Zoisite occurs as prismatic, orthorhombic (2/m 2/m 2/m) crystals or in massive form, being found in metamorphic and pegmatitic rock. Zoisite may be blue to violet, green, brown, pink, yellow, gray, or colorless. Blue crystals are known under the name Tanzanite.