Grossular

Good specimens of grossular usually come from metamorphosed limestones where calcium is abundant and iron absent. Its composition is Ca₃Al₂(SiO₄)₃. The other "ugrandite" garnets, andradite and uvarovite, have iron and chromium in place of the aluminum (Al). The garnets usually form good crystals with this form—round with 12 sides (dodecahedral)—or with 24 sides (trapezohedral). Grossular is usually green, but it may also be colorless through yellow, red and brown. The yellow-brown variety, which contains some iron, is known in the trade as essonite, hessonite, cinnamon stone, hyacinth or jacinth.