Ioliet 4x2 mm Marquise ± 0.06 CT. Color: Fine Violet Clarity: Clean Luster: Outstanding Origin: Africa Hardness: 7 - 7.5 Specific Gravity: 2.3 Refractive Index: 1.52 - 1.57 Chemical Composition: Mg2Al4Si5O18, Magnesium Aluminum Silicate Crystal Structure: Orthorhombic Treatment: None