#604. Lab Spinel Aquamarine - Sapphire - Blue Zircon Assortment, Safe to Fire...............
Sapphire Blue, Aquamarine and Blue Zircon Hardness: 8.0 Refractive index: 1.728 Specific Gravity: 3.64 Dispersion: .020 Heat Sensitivity: None Hard, durable and great colors.
Metal Clay, safe to fire. Test Results, Silver 1200F-1HR, Silver 1475F-1HR, Bronze 1525F-2HR, Copper 1778F-30min. Safe to use torch and safe to use carbon