Properties of Natural and Synthetic Diamonds Hardness = 10 Refractive index = 2.42 (Dispersion = 0.044 Internal inclusions such as feathers, clouds, veils, pinpoints, etc. Thermal conductivity (standard test used to differentiate diamonds from other colorless, high refractive gemstones, such as cubic zirconia). Platinum Yellow Diamond Ring Regular price: $15,000.00 Sale price: $14,500.00