Mahogany Obsidian
Obsidian (Volcanic glass containing Magnetite/Hematite) · Semi-Precious Gemstone / Decorative Stone
Crystal System
Amorphous (Non-crystalline, glassy structure with no internal lattice)
Mineral Group
Volcanic Glass (Silicate-rich)
Chemical Formula
70–75% SiO2, plus MgO, Fe3O4 (Magnetite) or Fe2O3 (Hematite)
Formation Process
Igneous: Forms when felsic lava cools rapidly with minimal crystal growth; reddish streaks are from Hematite oxidation
About This Crystal
An opaque, glassy material featuring deep reddish-brown (mahogany) swirls or splotches against a black base. It has a vitreous (glassy) luster and a smooth, curved surface when carved.
Physical Characteristics
Color: Black and reddish-brown; Streak: White; Cleavage: None; Fracture: Conchoidal (shell-like curves); Specific Gravity: 2.35–2.6; Fluorescence: Generally inert
Optical Properties
Refractive Index: 1.48–1.51; Birefringence: None (Isotropic/Singly Refractive); Pleochroism: None; Optical phenomena: None in this variety
Hardness & Durability
Origin Region
Western United States (Oregon, Arizona), Mexico, Armenia, and Japan
Hardness & Durability
Mohs Hardness: 5.0 to 5.5; Toughness: Brittle (easily chipped); Sensitivity: Stable to light but sensitive to abrupt temperature changes and hard impacts
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid ultrasonic cleaners and harsh chemicals; store separately to prevent scratching from harder stones like quartz
Rarity & Value
Common; Value is determined primarily by the quality of the carving and the balance of color; generally inexpensive ($5–$25 for small carvings); rarely treated
Special Characteristics
Displays distinctive reddish-brown inclusions of Hematite or Magnetite that create the signature 'mahogany' pattern; produces sharp edges when fractured
Lore & History
Used historically by ancient cultures for tools, weaponry, and mirrors; traditionally associated with grounding, protection, and strength in metaphysical lore