Black Obsidian
Volcanic Glass (Obsidian) · Semi-Precious Gemstone / Decorative Stone
Crystal System
Amorphous (Non-crystalline)
Mineral Group
Mineraloid
Chemical Formula
SiO2 (Silicon Dioxide with various impurities and iron/magnesium oxides)
Formation Process
Igneous (felsic lava extruded from a volcano cools rapidly without sufficient time for crystal growth)
About This Crystal
A smooth, tumbled, pitch-black stone with a vitreous to glossy luster and opaque transparency, featuring a small natural or impact indentation showing a slightly lighter matrix.
Physical Characteristics
Color is jet black, streak is white, cleavage is absent, fracture is distinctly conchoidal, specific gravity is approximately 2.35 to 2.50, and tenacity is brittle.
Optical Properties
Isotropic (singly refractive) with a refractive index of approximately 1.48 to 1.51, lacking pleochroism or birefringence due to its amorphous structure.
Hardness & Durability
Origin Region
Global distribution including USA, Mexico, Iceland, Italy, Japan, and Peru
Hardness & Durability
Mohs hardness of 5 to 5.5, moderate toughness, sensitive to sharp impacts which cause brittle conchoidal fracturing.
Care & Maintenance
Clean with warm soapy water and a soft cloth, avoid harsh chemicals or ultrasonic cleaners, and store separately to prevent scratching softer stones.
Rarity & Value
Common, affordable, and widely accessible for tumbled stones and jewelry, with value varying mainly by special optical varieties like sheen or snowflake patterns.
Special Characteristics
Breaks with extremely sharp conchoidal edges historically used for cutting tools, and sometimes exhibits chatoyancy (sheen obsidian) or snowflake patterns.
Lore & History
Historically used in ancient Mesoamerican cultures for weapons and mirrors, commonly associated in modern crystal healing with grounding and protection against negativity.