Green Obsidian
Volcanic Glass (Natural Glass) · Semi-Precious Gemstone and Decorative Stone
Crystal System
Amorphous (Non-crystalline)
Mineral Group
Mineraloid
Chemical Formula
SiO2 with various impurities and inclusions (predominantly silica)
Formation Process
Igneous, formed as an extrusive volcanic glass when felsic lava extruded from a volcano cools rapidly with minimal crystal growth.
About This Crystal
This is a polished, tumbled specimen of a vibrant deep green color. It exhibits a vitreous to greasy luster with high transparency in areas where light penetrates directly. The surface shows minor scratches typical of a softer tumbled stone, and a bright internal reflection highlights its rich emerald-green tone blending into darker regions.
Physical Characteristics
Color is a deep vibrant green with no visible streak (leaves no streak as it is amorphous). Cleavage is absent; fracture is distinctly conchoidal, yielding very sharp edges. Specific gravity is approximately 2.35 to 2.60. Tenacity is brittle.
Optical Properties
Isotropic (singly refractive) due to its amorphous structure. Refractive index is approximately 1.48 to 1.51. No pleochroism or birefringence.
Hardness & Durability
Origin Region
Mexico, United States (Oregon, Utah, Arizona), Iceland, Italy, and Japan. Forms in areas with recent volcanic activity and rhyolitic lava flows.
Hardness & Durability
Mohs hardness of 5 to 5.5. It is relatively brittle and can be scratched by quartz and harder minerals. Moderately suitable for jewelry if set in protective mountings.
Care & Maintenance
Clean with warm soapy water and a soft cloth. Avoid harsh chemical cleaners, ultrasonic cleaners, and sudden extreme temperature changes. Store separately from harder gemstones to prevent scratching.
Rarity & Value
Common to uncommon depending on the specific color variety. Green obsidian sold commercially is often man-made glass (slag glass), though natural green obsidian does exist in limited quantities. Value is generally low to moderate for tumbled specimens.
Special Characteristics
Displays a sharp conchoidal fracture and a vitreous luster. Colored green typically due to the inclusion of microscopic mineral crystals or iron/magnesium nanoparticles, though much of the brightly colored obsidian on the market is artificial glass.
Lore & History
In crystal healing and metaphysical practices, green obsidian is traditionally associated with the heart chakra, believed to promote emotional healing, compassion, and the release of emotional blockages. Note that these are traditional cultural beliefs and not scientifically validated claims.