mineral

Rough Ruby (Corundum) in Zoisite Matrix

Al2O3 (Aluminum Oxide) with Ca2Al3(SiO4)3(OH)

AI-generated identification · may be incorrect

Hardness: 9.0 (Ruby) / 6.0-7.0 (Zoisite); Color: Purplish-red with green or white mottling; Luster: Vitreous to sub-adamantine; Crystal Structure: Hexagonal (Trigonal); Cleavage: None (Ruby) / Perfect (Zoisite); Specific Gravity: 3.9-4.1

Hardness: 9
Color: Purplish-red with green or white mottling
Luster: Vitreous to sub-adamantine

Identified March 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed through regional metamorphism or hydrothermal activity where aluminum-rich fluids interact with low-silica rocks. Most commonly found in Pre-Cambrian metamorphic belts, often associated with gabbro or schist.

Uses & applications

Primarily used for lapidary work, ornamental carvings, tumbled stones, and as a collector's specimen. Lower-grade specimens are used in industrial abrasives.

Geological facts

Ruby is the second hardest natural substance on Earth after diamond. While high-quality ruby is a precious gemstone, the opaque variety seen here is often called 'common ruby' or 'ruby-in-zoisite' (Anyolite) when found with green zoisite.

Field identification & locations

Identify in the field by its extreme hardness (cannot be scratched by steel) and distinct purplish-pink 'pigeon blood' hue. Often shows a characteristic granular appearance when found in matrix. Major deposits located in Tanzania, India, and Myanmar.