crystals have a hexagonal prismatic habit, they are semitransparent or transparent and contain numerous fractures and inclusions. The best stones have a velvety deep green colour. In general, the crystals are not large, but may reach 1.5 cm in length. Rare crystals pf 3 to 5 cm are considered as very large. Faceted stones generally weigh up to 1.5 - 2 ct.