Mahogany Obsidian
Volcanic glass (silica-rich, iron-stained)
A natural volcanic glass with rich brown and black mahogany-like swirls created by iron oxide inclusions.
- Mohs hardness
- 5-5.5
- Color
- Brown to reddish-brown with black bands or patches
- Type
- igneous
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Overview
Mahogany obsidian is a variety of obsidian, the natural glass formed from rapidly cooled, silica-rich lava. Its distinctive reddish-brown and black mottled or banded coloring resembles polished mahogany wood, hence the name.
The brown and red tones come from tiny inclusions of iron oxide (hematite and magnetite) suspended in the otherwise dark glass, while black areas are pure obsidian. Swirls and bands record how the molten glass flowed before it froze.
Like all obsidian it is amorphous (non-crystalline), breaks with a sharp conchoidal fracture, and takes a high polish, making it popular for cabochons, beads, and carved ornaments as well as a favorite of crystal enthusiasts.
Formation & geology
Mahogany obsidian forms the same way as ordinary obsidian: felsic (high-silica) lava such as rhyolite is extruded and cooled so quickly that atoms cannot organize into crystals, freezing into glass instead. This typically happens at the chilled margins of lava flows and domes.
The characteristic brown coloring develops where iron-bearing minerals oxidize and form microscopic hematite inclusions within the glass, often concentrated in flow bands that create the mahogany pattern.
It is found in volcanic regions worldwide, with notable sources in the western United States (Oregon, Nevada, California, Arizona, Utah), Mexico, and other areas with rhyolitic volcanism.
How to identify it
Look for a glassy stone with rich brown to reddish-brown swirls, patches, or bands mixed with black. It has a vitreous (glassy) luster and breaks with smooth, curved conchoidal fractures and sharp edges.
Hardness is about 5-5.5, and it shows no crystal structure, cleavage, or visible grains. Held to light, thin edges may be translucent brown.
Look-alikes include mahogany-colored jasper (which is crystalline, opaque, harder at 7, and does not show glassy conchoidal fracture), petrified wood (shows wood grain and cell structure), and goldstone (a man-made glass with sparkly copper flecks). The glassy fracture plus brown-and-black banding identifies mahogany obsidian.
Uses & significance
Mahogany obsidian is mainly a lapidary and ornamental material, cut into cabochons, beads, spheres, pendants, and carved figurines that show off its woodgrain-like patterning when polished. Its sharp conchoidal fracture also made obsidian, including this variety, useful historically for tools, blades, and arrowheads.
It is too soft and brittle for hard-wearing ring stones but works well in pendants, earrings, and display pieces.
In metaphysical practice mahogany obsidian is promoted as a grounding, protective stone for strength and stability; these are spiritual beliefs rather than scientific properties. Its real appeal lies in its attractive, affordable, and easily polished glass.
Frequently asked questions
What makes mahogany obsidian brown?
Microscopic inclusions of iron oxide such as hematite within the volcanic glass produce the reddish-brown color, while pure glass forms the black areas, creating the mahogany pattern.
Is mahogany obsidian natural or man-made?
It is natural volcanic glass; the brown banding forms during cooling. (Don't confuse it with goldstone, which is a man-made sparkly glass.)
Is mahogany obsidian a crystal?
Technically no. Like all obsidian it is amorphous volcanic glass with no crystalline structure, even though it is sold within the crystal and lapidary trade.
How do I tell mahogany obsidian from jasper?
Obsidian is glassy, breaks with smooth conchoidal fractures, and is translucent on thin edges, while mahogany jasper is opaque, harder, and has a grainy, crystalline (chalcedony) texture.
Mahogany Obsidian guides
In-depth guides for identifying, valuing, and understanding Mahogany Obsidian.
Mahogany Obsidian identified by the community
Real specimens identified with Rock Identifier.
