Obsidian
A naturally occurring volcanic glass formed when lava cools rapidly.
Physical & Optical Properties
RI Range1.480–1.510
SG Range2.30–2.60
SG Typical2.40
Hardness (Mohs)5–5.5
Crystal SystemAmorphous
Optic CharacterSR (Singly Refractive)
Dispersion0.010
Fluorescence LWInert
Fluorescence SWInert
Chelsea FilterInert
PleochroismNone
ColorsBlack, Brown, Green, Multi
SpeciesNatural Glass
Key Differentiators
- Amorphous volcanic glass
- Conchoidal fracture
- Low RI and SG
Treatments
- Surface Coating (galaxy obsidian, iridescent finish)
- Dyeing (enhanced color or sheen)
Price Context
Natural — low ($/ct)$1
Natural — high ($/ct)$5
NotePer carat; volcanic glass; rainbow sheen and snowflake varieties command modest premium
Price context is approximate. GemID is not an appraisal tool. Results are indicators, not certified valuations.
About Obsidian
A naturally occurring volcanic glass formed when lava cools rapidly.
Identifying a obsidian? GemID walks through these tests in order — RI, SG, fluorescence, and more.
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