igneous
Mahogany Obsidian
Volcanic Glass (Amorphous Silicon Dioxide with Hematite inclusions)
Hardness: 5-5.5 (Mohs scale), Color: Black/red-brown streaks, Luster: Vitreous/glassy, Structure: Amorphous (non-crystalline), Cleavage: None (conchoidal fracture), SG: 2.3-2.6
- Hardness
- 5-5
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Physical properties
Hardness: 5-5.5 (Mohs scale), Color: Black/red-brown streaks, Luster: Vitreous/glassy, Structure: Amorphous (non-crystalline), Cleavage: None (conchoidal fracture), SG: 2.3-2.6
Formation & geological history
Forms from the extremely rapid cooling of felsic lava, preventing crystal growth. The reddish-brown color comes from inclusions of Magnetite or Hematite (iron oxide).
Uses & applications
Used in ornamental jewelry, decorative items, healing stone collections, and historically for making sharp tools like arrowheads due to its conchoidal fracture.
Geological facts
This specimen appears to be worked or knapped, resembling an archaeological artifact or a reproduction arrowhead. Obsidian was prized in the Stone Age for producing edges sharper than modern surgical scalpels.
Field identification & locations
Identify by its glassy texture, sharp edges, and unique swirled reddish-brown and black patterns. Common in volcanic regions of Oregon, Mexico, and the western USA.
