Chemical composition -- An oxide of magnesium, aluminum, silicon, and boron, with hydroxyl.
Color -- Usually shades of green or brown.
Optics -- R.I 1.66-1.70.
Durability -- Hardness 6-7.
Crystal structure -- Orthorhombic.
Specific Gravity -- 3.27-3.45.
Sources -- Kenya, Myanmar (Burma), Sri Lanka, Canada. Kornerupine is a rather scarce collector's item and very rare in asteriated (star) material. Light green stones from Kenya are particularly attractive.