Rainbow Obsidian
Amorphous Volcanic Glass with Mineral Inclusions · Semi-Precious Gemstone / Decorative Stone
Crystal System
Amorphous (Non-crystalline); massive habit with conchoidal fracture
Mineral Group
Silicates (specifically Volcanic Glass)
Chemical Formula
70–75% SiO2, plus MgO, Fe3O4
Formation Process
Igneous/Extrusive; formed from rapid cooling of high-silica lava which prevents crystal growth, creating natural glass.
About This Crystal
An opaque, black natural glass that displays colorful iridescent bands (purple, green, or gold) when polished and exposed to bright light. It has a vitreous luster and a smooth, glassy surface.
Physical Characteristics
Color: Black with iridescent sheen; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.35–2.60; Fluorescence: Generally none.
Optical Properties
Singly refractive; exhibit iridescence caused by light refraction from microscopic bubbles of water or oriented inclusions of magnetite/pyroxene.
Hardness & Durability
Origin Region
Mexico (notably Jalisco), United States (Oregon, California), Iceland; found in volcanic regions.
Hardness & Durability
Mohs hardness: 5.0 to 5.5; Brittle tenacity with very low toughness; sensitive to pressure and sharp blows.
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid ultrasonic cleaners, steam, and harsh chemicals. Store separately to prevent scratching from harder stones.
Rarity & Value
Uncommon; value is determined by the clarity and vibrancy of the rainbow colors, surface area of the effect, and quality of the carving.
Special Characteristics
Displays rainbow-colored iridescence or 'sheen' when viewed at specific angles under strong light; contains microscopic inclusions of water/gas.
Lore & History
Historically used for making sharp tools, mirrors, and weapons by Aztecs and Maya. Traditionally associated with protection, emotional healing, and the root chakra in modern lore.