Obsidian
Volcanic Glass · Semi-Precious Gemstone and Mineral Specimen
Crystal System
Amorphous (no true crystal system)
Mineral Group
Mineraloid
Chemical Formula
SiO2 with varying impurities (mostly Fe and Mg)
Formation Process
Extrusive igneous process formed by the rapid cooling of viscous lava rich in silica
About This Crystal
Dark, glassy, smooth-textured black material showing high vitreous luster and conchoidal fracture
Physical Characteristics
Black or dark brown body color, white streak, conchoidal fracture with extremely sharp edges, no cleavage, specific gravity around 2.35 to 2.45, brittle tenacity
Optical Properties
Singly refractive, isotropic, vitreous luster, opaque except in very thin splinters
Hardness & Durability
Origin Region
Found globally near active volcanic regions including USA, Mexico, Iceland, and Italy
Hardness & Durability
Mohs hardness of 5 to 5.5, brittle toughness, sensitive to sharp impacts, moderate durability for jewelry
Care & Maintenance
Clean with warm soapy water, store separately to avoid scratching softer materials, avoid harsh acids and impact
Rarity & Value
Common, affordable, value depends on special sheens or inclusions like snowflake or golden obsidian
Special Characteristics
May exhibit sheen effects like rainbow, golden, or silver sheen caused by microscopic gas bubbles or crystal inclusions
Lore & History
Historically used by ancient civilizations for arrowheads, cutting tools, and mirrors; used in modern crystal healing for protection and grounding