Black Obsidian
Obsidian (Volcanic Glass) · Semi-Precious Gemstone / Decorative Stone
Crystal System
Amorphous (Non-crystalline) / No crystal habit
Mineral Group
Silicates / Mineraloid (Volcanic Glass)
Chemical Formula
SiO2 (70–75%) with MgO, Fe3O4
Formation Process
Igneous: Extrusive volcanic glass formed by the rapid cooling of silica-rich rhyolitic lava which prevents crystallization.
About This Crystal
Jet-black, opaque to slightly translucent at thin edges. Features a high vitreous (glassy) luster with a smooth, polished surface carved into a crescent moon shape.
Physical Characteristics
Color: Pitch black; Streak: White; Cleavage: None; Fracture: Conchoidal (shell-like curves); Specific Gravity: 2.35–2.60; Fluorescence: Generally inert.
Optical Properties
Isotropic (Singly Refractive); Refractive Index: 1.450–1.550; Luster: Vitreous; No pleochroism due to amorphous structure.
Hardness & Durability
Origin Region
Mexico (Jalisco), USA (Oregon, California), Iceland, and Japan; found in volcanic fields.
Hardness & Durability
Mohs Hardness: 5.0–5.5; Toughness: Brittle; Sensitivity: Vulnerable to scratches and sharp impacts; high thermal shock sensitivity.
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid ultrasonic cleaners and harsh chemicals. Store separately from harder stones like quartz or topaz.
Rarity & Value
Common; Value is determined by carving quality and size. Very affordable; treatments are rare, though some black glass can be sold as obsidian.
Special Characteristics
Exhibits perfectly conchoidal fracture which allows for extremely sharp edges; may show 'Rainbow' or 'Silver' sheen in specific varieties (not visible here).
Lore & History
Historically used by Mesoamerican cultures for sacrificial blades and mirrors. Spiritually associated with the Root Chakra, protection, and 'scrying'.