16.6.1.10: Tigereye Last updated Save as PDF Page ID4125 Contributed by gemologyGemology Project Agate Chemical composition SiO2 Silicon dioxide Crystal system Trigonal Habit Aggregate Fracture Conchoidal Hardness 6.5-7 Refractive index ± 1.55 Specific gravity 2.60 Lustre Vitreous Figure \(\PageIndex{1}\)