Black Obsidian
Volcanic Glass (Obsidian) · Decorative Stone / Semi-Precious Gemstone
Crystal System
Amorphous (Non-crystalline)
Mineral Group
Mineraloid
Chemical Formula
SiO2 (Silicon Dioxide with various impurities and iron/magnesium oxides)
Formation Process
Extrusive Igneous (formed by the rapid cooling of felsic lava)
About This Crystal
This is a polished stone cut and shaped into a six-sided hexagonal tower with a pyramidal apex. The specimen exhibits a solid jet-black color with a high-gloss, reflective vitreous luster characteristic of volcanic glass. It is entirely opaque with smooth, expertly cut and polished facets.
Physical Characteristics
Color is deep black, streak is white, cleavage is absent due to its amorphous structure, fracture is distinctly conchoidal, specific gravity is approximately 2.35 to 2.60, and tenacity is brittle.
Optical Properties
Isotropic (singly refractive), refractive index is roughly 1.48 to 1.51, completely opaque in bulk form with no pleochroism.
Hardness & Durability
Origin Region
United States (Oregon, California), Mexico, Iceland, Italy, Japan
Hardness & Durability
Mohs hardness is 5 to 5.5, making it relatively soft and prone to scratching by harder minerals like quartz. It has moderate to low toughness and can shatter upon sharp impact.
Care & Maintenance
Clean with warm soapy water and a soft cloth. Avoid ultrasonic or steam cleaners, harsh chemicals, and prolonged exposure to direct sunlight. Store separately from harder gemstones to prevent scratching.
Rarity & Value
Common, widely available worldwide. Value is generally low to moderate depending on size, craftsmanship, and any special optical phenomena like sheen or rainbow effects. Treatments are rare since the material is abundant.
Special Characteristics
Forms as a natural volcanic glass without a true crystal lattice, resulting in extremely sharp conchoidal fracture edges historically used for cutting tools.
Lore & History
Used extensively by ancient civilizations such as the Aztecs and Mayans for tools, weapons, and ritual mirrors. In modern metaphysical practices, black obsidian is traditionally associated with the Root Chakra and is believed to serve as a powerful grounding and protective stone that shields against negativity.