Yellow-Green Obsidian Identification Guide
How to identify yellow-green obsidian volcanic glass by its glassy luster, conchoidal fracture, and lack of crystals, plus separating it from glass imitations.
Read the full Yellow-Green Obsidian encyclopedia entry →
What Yellow-Green Obsidian Looks Like
Yellow-Green Obsidian is a colored volcanic glass formed from rapidly cooled, silica-rich lava. Its yellow-green tint comes from trace iron and other elements; note that much vividly colored "obsidian" in the market is actually manufactured glass, so testing matters.
- Color: yellowish-green, olive, with possible darker or smoky zones
- Luster: bright vitreous (glassy)
- Transparency: translucent to nearly opaque depending on thickness
- Habit: amorphous (no crystals); massive nodules and chunks with smooth curved surfaces
Step-by-Step Field ID Checklist
- Look for glassy luster — a smooth, reflective, water-like sheen.
- Check fracture — obsidian breaks with sharp conchoidal (shell-shaped) curves and razor edges.
- Confirm no crystals — it should be uniform glass; no grains, no banding lines of mineral.
- Test hardness — scratches with effort around Mohs 5–5.5 (a steel knife may scratch it).
- Look for bubbles/inclusions — natural obsidian may show stretched gas bubbles or microlite swirls; perfectly clean glass with round bubbles suggests manufactured glass.
Key Diagnostic Tests
- Mohs hardness: ~5–5.5; softer than quartz, can be scratched by hardened steel.
- Streak: white.
- Fracture: conchoidal, producing very sharp edges.
- Density: ~2.35–2.6 g/cm³, relatively light.
- Magnetism/acid: non-magnetic; inert to acid.
Common Look-Alikes and How to Tell Them Apart
- Manufactured/slag glass: the biggest concern. Look for uniform color, perfectly spherical bubbles, and mold marks; natural obsidian often has flow swirls, microlites, and irregular bubble shapes.
- Moldavite (tektite): also green glass but pitted/etched natural surface and a more bottle-green, mossy color; specific gravity differs slightly.
- Green chalcedony/jasper: harder (Mohs 7), waxy not glassy, microcrystalline rather than amorphous.
- Green fluorite: has cubic cleavage and is softer (Mohs 4); obsidian has conchoidal fracture.
- Green bottle glass: essentially identical chemically; relies on provenance and inclusion character to separate.
Where It Is Typically Found
Natural obsidian forms at the margins of rhyolitic lava flows and domes in volcanic regions—classic areas include the western United States (Oregon, California, Idaho, Arizona), Mexico, Iceland, and Italy. Because naturally yellow-green obsidian is uncommon, treat brightly colored specimens with caution and verify with the glassy, conchoidal, low-hardness tests and inclusion examination.
Frequently asked questions
Is yellow-green obsidian natural or man-made?
Some is natural volcanic glass, but a large amount of vividly colored "obsidian" sold is manufactured glass. Check for natural flow swirls, microlite inclusions, and irregular bubbles; uniform color with perfectly round bubbles and mold seams indicates man-made glass.
How can you tell if it's real obsidian?
Real obsidian is a glassy, amorphous volcanic glass with conchoidal fracture, very sharp edges, hardness around 5–5.5, a white streak, and no crystal structure. Natural specimens often show stretched bubbles or microscopic crystallites.
What does yellow-green obsidian look like?
It appears as smooth, glassy yellowish-green to olive volcanic glass, translucent to nearly opaque, with a bright vitreous sheen and curved, sharp-edged fracture surfaces.
Yellow-green obsidian vs moldavite: what's the difference?
Moldavite is a tektite with a distinctive pitted, etched natural surface and a mossy bottle-green color, while obsidian is smoother volcanic glass. Surface texture and provenance are the key distinguishers.
Yellow-Green Obsidian identified by the community
Recent Yellow-Green Obsidian specimens identified with Rock Identifier.
