Chroom Tourmalijn ± 0.03 CT. 1.5 mm Square Cut Color: Nice Chrome Green Clarity: Clean To Eye Clean Luster: Blazing Origin: Africa Hardness: 7 - 7.5 Specific Gravity: 3.0+ Refractive Index: 1.62 - 1.68 Chemical Composition: Na(Li,Al)3Al6Si6O18(BO3)3 (OH)4, Sodium Lithium Aluminum Boro-Silicate Hydroxide Crystal Structure: Trigonal Treatment: None