Midnight Obsidian
Volcanic glass (SiO2-rich)
A trade name for deep, solid black obsidian, natural volcanic glass prized for its uniform jet-black color and glassy luster.
- Mohs hardness
- 5-6
- Color
- Deep, solid black
- Type
- igneous
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Overview
Midnight Obsidian is a marketing name for richly black, opaque obsidian — natural volcanic glass formed from rapidly cooled felsic lava. The deep color comes from finely dispersed iron and magnesium oxides within the glass.
As an amorphous glass it has no crystal structure; it breaks with the smooth, curved conchoidal fracture that made obsidian valuable for ancient tools and weapons.
The "midnight" label simply emphasizes an especially dark, even black appearance, sometimes with a faint sheen, distinguishing it in the trade from rainbow, snowflake, or mahogany varieties.
Formation & geology
Midnight Obsidian forms when silica-rich rhyolitic lava cools so quickly that atoms cannot organize into crystals, freezing into glass. This typically happens at the chilled margins of lava flows and volcanic domes.
Low water content in the magma favors thick, glassy obsidian rather than frothy pumice. Trace iron oxides dispersed through the melt give the deep black color.
It occurs worldwide in young felsic volcanic regions, including Mexico, the western United States (Oregon, California), Iceland, Armenia, and Turkey.
How to identify it
Look for a solid black, glassy stone with a bright vitreous luster, translucent dark edges when held to strong light, and conchoidal fracture producing curved, razor-sharp surfaces. Hardness is 5-6 and streak is white.
It is warm to the touch faster than glass-like minerals and lacks any crystalline cleavage.
Distinguish from black tourmaline and onyx (both crystalline, with different fracture) and from dark basalt (dull and stony, not glassy). Manufactured black glass can mimic it; gas-bubble alignment, flow lines, and natural surface help confirm true obsidian.
Uses & significance
Midnight/black obsidian is widely used for cabochons, beads, spheres, carvings, and jewelry where a deep glossy black is wanted. It polishes to a mirror finish.
Archaeologically and even in modern surgery, obsidian's sharp conchoidal edge made it valuable for blades and scalpels.
In metaphysical practice black obsidian is one of the most popular "protection" and grounding stones, used for scrying mirrors; these uses are traditional beliefs, not scientifically demonstrated.
Frequently asked questions
Is Midnight Obsidian a special type of obsidian?
It is mainly a trade name for deep, solid black obsidian; mineralogically it is ordinary black volcanic glass.
What makes obsidian black?
Finely dispersed iron and magnesium oxides within the glass absorb light, producing the deep black color.
Is black obsidian sharp?
Yes. It fractures conchoidally into extremely sharp edges, which is why it was used historically for cutting tools.
How can I tell it from black glass or onyx?
Obsidian is glassy with conchoidal fracture and translucent thin edges; onyx is crystalline chalcedony, and manufactured glass often shows mold seams or ordered bubbles.
Midnight Obsidian guides
In-depth guides for identifying, valuing, and understanding Midnight Obsidian.
Midnight Obsidian identified by the community
Real specimens identified with Rock Identifier.
