Ruby
Corundum var. Ruby · Precious Gemstone
Crystal System
Trigonal; Hexagonal scalenohedral; typically forms as hexagonal prisms or tablets
Mineral Group
Oxides (Hematite group)
Chemical Formula
Al2O3 (with Cr3+ Trace Impurities)
Formation Process
Forms under high temperature and high pressure in aluminum-rich metamorphic rocks (like marble) or in igneous rocks like basalt.
About This Crystal
Strongly saturated 'pigeon blood' red to pinkish-red hue. It exhibits a vitreous luster and is transparent in high-quality specimens with typical 'silk' (rutile) inclusions or liquid-filled fractures.
Physical Characteristics
Color: Red to purplish-red; Streak: White; Cleavage: None (has parting); Fracture: Conchoidal or splintery; Specific Gravity: 3.97-4.05; Fluorescence: Strong red under longwave UV (especially in low-iron specimens).
Optical Properties
Refractive Index: 1.762-1.770; Birefringence: 0.008; Pleochroism: Strong (purplish-red to orangey-red); Singly refractive; high luster.
Hardness & Durability
Origin Region
Notable sources include Myanmar (Burma), Mozambique, Thailand, Madagascar, and Vietnam. Found in regional metamorphic rocks such as marble or as secondary alluvial deposits.
Hardness & Durability
Mohs Hardness: 9; Toughness: Excellent; Stability: High (stable to light and most chemicals, sensitive to extreme heat if glass-filled).
Care & Maintenance
Clean with warm soapy water or ultrasonic cleaner (unless glass-filled). Store separately to avoid scratching softer stones. Avoid hydrofluoric acid.
Rarity & Value
Rare to Very Rare for high-quality natural stones. Value is determined by 'Color, Clarity, Cut, and Carat.' Treatments like heat are common, while glass-filling significantly lowers value.
Special Characteristics
Can exhibit asterism (star ruby) or strong red fluorescence. Inclusions often include rutile needles (silk), crystals, and feathers.
Lore & History
Known as the 'King of Precious Stones' in Sanskrit. Historically symbolized passion, protection, and prosperity. Traditionally associated with the base/root chakra and the sun.