Labradoriet (Rainbow Facet) ± 0.15 CT. 4x3 mm Oval Cut Color: Fine Gray with Rainbow Luster Clarity: Transparent Luster: Outstanding Origin: Africa Hardness: 6 - 6.5 Specific Gravity: 2.70 - 2.74 Refractive Index: 1.55 - 1.75 Chemical Composition: CaNa(Al,Si)AlSi2O8, Calcium Sodium Aluminum Silicate Crystal Structure: Triclinic Treatment: None