💚 Emerald Optics Lab: Refractive Index 1.565-1.602 (typically 1.577-1.583), Dispersion and Brilliance of a Cut Emerald

Emerald (Be3Al2Si6O18 with Cr3+/V3+): refractive index 1.565-1.602 (typically 1.577-1.583), Mohs hardness 7.5-8, dispersion 0.014. Emerald is the green variety of beryl, a beryllium aluminium silicate, coloured by chromium and sometimes vanadium. It is relatively hard (7.5 to 8) but brittle because almost every emerald contains fractures and inclusions, which is why the protective step cut that bears its name was developed.