Black Obsidian
Natural Volcanic Glass · Decorative Stone / Mineral Specimen
Crystal System
Amorphous (Non-crystalline)
Mineral Group
Mineraloid
Chemical Formula
SiO2 with varying amounts of Fe and Mg
Formation Process
Igneous, formed from rapidly cooling felsic lava where chemical constituents do not have time to crystalize
About This Crystal
Tumbled, dark black smooth stone with glossy luster, displaying minor translucent brownish-gray margins along the edges
Physical Characteristics
Black body color, white streak, conchoidal fracture, specific gravity of approximately 2.35 to 2.45, brittle tenacity, vitreous luster
Optical Properties
Isotropic, singly refractive, opaque to translucent in thin edges
Hardness & Durability
Origin Region
Found globally in areas with recent volcanic activity, including USA, Mexico, Iceland, and Italy
Hardness & Durability
Mohs hardness of 5 to 5.5, brittle with sharp conchoidal fracture, poor durability for daily wear rings
Care & Maintenance
Clean with mild soap and warm water, avoid harsh chemicals and ultrasonic cleaners, store separately to avoid scratching softer stones
Rarity & Value
Common, affordable price range, widely accessible as tumbled stones or jewelry
Special Characteristics
May exhibit a sheen or iridescence when inclusions of magnetite or gas bubbles are present (though not prominently visible here)
Lore & History
Historically used in prehistoric times for making arrowheads and cutting tools; traditionally associated with protection, grounding, and clearing negative energy in crystal healing practices