Raw Sapphire / Corundum

Hardness 9 on Mohs scale, vitreous to adamantine luster, trigonal/hexagonal crystal system, basal parting, color ranges from greyish-blue, brownish-tan to blue, specific gravity ~4.0

Formed through regional or contact metamorphism of aluminum-rich silica-poor rocks like marble and schist, or in silica-undersaturated igneous rocks like syenites and pegmatites.

Cut into gemstones for high-end jewelry, used as an industrial abrasive, used in scratch-resistant optical windows, and collected as mineral specimens.

Corundum is the second hardest natural substance known after diamond. Non-red gem varieties of corundum are called sapphires, while red varieties are known as rubies.

Identified in the field by its extreme hardness (scratches quartz and topaz), high density, hexagonal growth striations, and characteristic barrel-like or prismatic crystal habits. Found commonly in Sri Lanka, Madagascar, Myanmar, Kashmir, Australia, and Montana, USA.