IGI Report Number: 746504147 • Species/Variety: Natural Topaz / Blue Topaz • Shape & Cut: Cut Cornered Rectangular Mixed Cut • Weight: 24.00 ct • Measurements: 18.36 × 13.57 × 10.62 mm • Color & Transparency: Blue, Transparent • Characteristics: Natural inclusions • Comments: Blue Topaz is commonly treated by irradiation followed by heat. Indicative evidence of treatment is typically lacking. • Optical & Physical Properties: • Refractive Index: 1.619 – 1.627 • Birefringence: 0.008 • Optic Character: Biaxial • Specific Gravity: 3.53