Ruby

Physical Properties

Hardness: 9 on Mohs scale; Color: Red (pigeon blood to pinkish-red); Luster: Vitreous to sub-adamantine; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (has parting); Specific Gravity: 3.97-4.05

Formation & Geological History

Formed in metamorphic rocks such as marble and schist, or in igneous rocks like basalt. Created through high pressure and temperature where aluminum thrives and silica is scarce. Most deposits are millions of years old.

Uses & Applications

Primarily used in high-end jewelry (faceted or cabochon), and industrially in lasers, watchmaking (jeweled movements), and precision instruments.

Geological Facts

The red color is caused by trace amounts of chromium. It is the birthstone for July and is the second hardest natural mineral after diamond. Some rubies exhibit asterism, creating a 6-rayed star.

Field Identification & Locations

Identify by its extreme hardness (cannot be scratched by steel or quartz) and distinct red fluorescence under UV light. Commonly found in Myanmar (Burma), Madagascar, Thailand, and Mozambique.

Identified on: 5/2/2026

Mode: Standard