Midnight Obsidian Identification Guide
How to identify Midnight Obsidian, a jet-black volcanic glass, by its vitreous luster, conchoidal fracture, hardness, and low density.
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What Midnight Obsidian Looks Like
Midnight Obsidian is a deep, uniform black volcanic glass. It is essentially classic black obsidian marketed under a name emphasizing its dark, even color. Unlike sheen or rainbow types, it shows little to no internal banding or iridescence.
- Color: Solid, inky black throughout.
- Luster: Bright vitreous (glassy), often mirror-like when polished.
- Transparency: Opaque in the mass; thin chips can be translucent brown-black.
- Habit/form: Massive, amorphous; no crystals, no cleavage.
Step-by-Step Field ID Checklist
- Look at the surface: A wet, glassy shine is the first clue it is glass, not a crystalline rock.
- Break or chip a corner (safely): Obsidian breaks with smooth, curved conchoidal fractures and produces wickedly sharp edges.
- Hold it to strong light: Thin edges glow translucent brown to gray; a fully opaque "black" with no glassiness suggests another material.
- Heft it: Obsidian feels lighter than an equal-size piece of dense black ore.
- Run the hardness and acid tests below.
Key Diagnostic Tests
- Mohs hardness: ~5–5.5. A steel knife may barely scratch it; quartz (7) scratches it easily.
- Streak: White to pale gray.
- Fracture: Conchoidal, with sharp cutting edges; no cleavage planes.
- Density: ~2.35–2.6 g/cm3 — light for a black stone.
- Acid: Inert to dilute HCl.
- Magnetism: None (rare iron-rich glass can be faintly attracted).
Common Look-Alikes and How to Tell Them Apart
- Apache tears: Also obsidian, but small rounded nodules that are translucent when held to light; Midnight Obsidian is larger, massive black.
- Black tourmaline (schorl): Striated prismatic crystals, hardness 7+, dull-to-vitreous but never glassy-flow; no conchoidal break.
- Hematite: Heavy, metallic, and leaves a red-brown streak.
- Black glass / slag: Mold seams, perfectly round bubbles, and sometimes greenish edges betray man-made origin.
- Jet: Very light, warm, brown streak, smells of coal when a hot point touches it.
- Black onyx: Harder (7), waxy luster, and microcrystalline (not glassy).
Where It Is Found
Black obsidian forms wherever felsic (rhyolitic) lava cools rapidly. Major sources include the western U.S. (Oregon, California, Idaho, Arizona, New Mexico), Mexico, Iceland, Italy (Lipari), and Armenia.
Frequently asked questions
How can you tell if Midnight Obsidian is real?
Genuine obsidian is glass: it has a vitreous luster, breaks with smooth conchoidal fractures and sharp edges, rates about 5–5.5 on Mohs, is light in the hand, and shows translucent brown-black thin edges against strong light. Mold seams and uniform round bubbles indicate man-made glass.
What does Midnight Obsidian look like?
It is a glossy, inky-black volcanic glass with a smooth, often mirror-like polished surface and no internal banding. Thin edges glow translucent when backlit.
Is Midnight Obsidian a crystal?
No. Obsidian is amorphous volcanic glass that cooled too fast to form crystals, so it has no crystal structure, no cleavage, and breaks conchoidally.
Midnight Obsidian vs black tourmaline?
Black tourmaline forms striated columnar crystals and is harder (7+), while Midnight Obsidian is a softer (5–5.5) structureless glass with conchoidal fracture.
Midnight Obsidian identified by the community
Recent Midnight Obsidian specimens identified with Rock Identifier.
