Chemical composition -- Magnesium aluminum borate.
Color -- Yellow to brown to pink.
Optics -- R.I 1.66-1.71.
Durability -- Hardness 6.5-7.
Crystal structure -- Orthorhombic.
Specific Gravity -- 3.47-3.50.
Sources -- The primary source is Sri Lanka, where gems of more than 100 carats have been found. Prior to 1952, sinhalite was thought to be brown peridot. Properly cut stones are quite attractive and very desirable in collections.