Zoisite and Ruby

Massive form of green Zoisite with tabular subhedral Ruby that has an adamantine lustre. Largest crystal face of the Ruby on the surface is measured at 1.9 cm by 2.5 cm. Zoisite (Ca2Al3Si3O12(OH)) can be grey, yellowish brown, greenish, pink (Thulite) or blue (Tanzanite) in colour. Lustre is vitreous and pearly on the cleavage and streak is white. Hardness is 6 to 6 1/2 and cleavage is good lengthwise. Zoisite is usually long prismatic crystals that have striations along the length of the crystal faces but can also be columnar, bladed, fibrous or compact. Corundum (Al2O3) has a variety of colours and when it is a deep red it is known as Ruby. Lustre can be vitreous or adamantine and streak is white. Hardness is 9 and specific gravity is high at 4.1. Corundum can be prismatic that is tapering but also pyramidal or tabular and the faces of the crystal are often striated.