Mahogany Obsidian
Volcanic Glass (variety: Mahogany Obsidian) · Semi-Precious Gemstone / Decorative Stone
Crystal System
Amorphous (Non-crystalline); lacks an ordered internal atomic structure. Habit is massive; often found in large flows or nodules.
Mineral Group
Silicates (specifically a natural volcanic glass/mineraloid)
Chemical Formula
SiO2 (approx. 70–75%) with inclusions of Fe2O3 (Hematite/Magnetite)
Formation Process
Igneous. Forms from the rapid cooling of silica-rich (rhyolitic) lava, preventing crystal growth. The mahogany pattern is created by oxidation of iron during solidification.
About This Crystal
An opaque volcanic glass featuring a deep reddish-brown to brick-red mahogany color swirled with black. It exhibits a vitreous to glassy luster and a smooth, uniform texture when polished.
Physical Characteristics
Color: Red-brown and black; Streak: White; Cleavage: None; Fracture: Conchoidal (shell-like); Specific Gravity: 2.3–2.6; Luster: Vitreous.
Optical Properties
Isotropic (singly refractive); Refractive Index: 1.45–1.55; Transparency: Opaque to translucent on thin edges; no pleochroism or birefringence.
Hardness & Durability
Origin Region
Primarily North America (Oregon, California, Utah, Mexico) and volcanic regions like Armenia and Japan.
Hardness & Durability
Mohs Hardness: 5.0–5.5; Toughness: Brittle (easily chips or cracks); Stability: Sensitive to high heat and rapid temperature changes.
Care & Maintenance
Clean with warm soapy water and a soft cloth. Avoid ultrasonic cleaners, steam, and harsh chemicals. Store separately from harder gemstones like quartz/topaz to prevent scratching.
Rarity & Value
Common; Value is generally low to moderate. Pricing depends on the boldness of the mahogany patterning and the quality of the carving or polish. Generally untreated.
Special Characteristics
Displays a distinctive mottled or banded pattern caused by the concentration of iron oxide (hematite) within the black glass matrix.
Lore & History
Historically used for making sharp tools, arrowheads, and mirrors. Metaphysically, it is regarded as a stone of protection and grounding, associated with the Root Chakra and used to release inner limitations.