Black Obsidian
Volcanic Glass (Obsidian) · Decorative Stone and Semi-Precious Gemstone
Crystal System
Amorphous (Non-crystalline)
Mineral Group
Mineraloid
Chemical Formula
SiO2 (Silicon Dioxide with variable impurities such as Fe and Mg)
Formation Process
Igneous (Extrusive volcanic activity, formed from felsic lava cooling rapidly without sufficient time for crystal growth)
About This Crystal
An amorphous, glassy rock displaying a deep jet-black color with a highly reflective, vitreous to glassy luster. It features sharp, curved conchoidal fracture surfaces that are smooth and glossy.
Physical Characteristics
Color is solid black, white streak, no cleavage, distinctly conchoidal fracture, specific gravity around 2.35 to 2.45, brittle tenacity, non-magnetic, and generally inert under UV light.
Optical Properties
Singly refractive (isotropic due to amorphous structure), refractive index is approximately 1.48 to 1.51, completely opaque in thick specimens though translucent to transparent in extremely thin edges.
Hardness & Durability
Origin Region
United States (Oregon, California), Mexico, Iceland, Italy, Japan, and Peru
Hardness & Durability
Mohs hardness of 5 to 5.5, low toughness due to extreme brittleness and sharp cleavage-like conchoidal fracturing, making it sensitive to heavy impacts.
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid harsh chemicals, ultrasonic cleaners, and hard drops that can shatter or scratch the glass surface.
Rarity & Value
Common; widely available and affordable, with value determined by size, unique sheens like golden or rainbow variants, and carving quality.
Special Characteristics
Displays perfect conchoidal fracture patterns capable of producing edges sharper than surgical steel, occasionally exhibiting iridescent sheens caused by microscopic gas bubble inclusions.
Lore & History
Historically used by ancient Mesoamerican civilizations like the Aztecs and Mayas to craft weapons, mirrors, and ritual tools. In modern metaphysical practices, it is considered a powerful grounding and protective stone associated with the Root Chakra.