Ruby (Pinkish-Red)

Physical Properties

Hardness: 9.0; Color: Pink to Pigeon-blood red; Luster: Adamantine to vitreous; Crystal structure: Trigonal/Hexagonal; Cleavage: None (has parting); Specific Gravity: 3.97-4.05

Formation & Geological History

Formed in metamorphic or igneous environments, specifically marble-hosted or basalt-hosted deposits. Can be millions of years old, often found in alluvial deposits where they weather out from host rock.

Uses & Applications

Primary use in high-end jewelry (birthstone for July). Historically used in watches and early lasers; industrial varieties are used for abrasives and precision instruments.

Geological Facts

Rubies are the rarest member of the corundum family. If the color is too light, the stone is classified as a Pink Sapphire rather than a Ruby. The presence of chromium gives it both its red color and its unique fluorescence.

Field Identification & Locations

Identify by hardness (9.0—scratches almost everything except diamond), distinct vitreous luster, and high specific gravity. Often shows 'silk' (fine rutile needle inclusions) or hexagonal growth lines under magnification.

Identified on: 4/14/2026

Mode: Standard