Obsidian is a naturally occurring volcanic glass formed when felsic lava cools rapidly with minimal crystal growth. It is famous for its conchoidal fracture, creating extremely sharp edges that have been used for cutting tools since antiquity.
Is this obsidian?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch obsidian with a known reference. Obsidian sits at Mohs 5-6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Obsidian leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Obsidian typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: black, dark green, mahogany, rainbow, sheen.
- 5Look at form & habitTypical habit: massive.
Often confused with
Obsidian vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside obsidian
Minerals reported to co-occur with obsidian. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SiO₂
- Mohs hardness
- 5-6
- Density
- 2.3-2.6 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal habit
- Massive
- Cleavage
- None
- Rarity
- Common
- Uses
- Lapidary, Ornamental, Collector
- Host rock
- Volcanic Rhyolitic Lava Flows
- Typical price
- $5-50 for typical specimens, higher for specific optical varieties like rainbow or snowflake
Where rockhounds find obsidian
15 mapped spotsClassic worldwide localities
- Mexico
- USA
- Iceland
- Italy
- Japan
U.S. states with obsidian
Each link opens a state-specific list of mapped rockhounding spots that produce obsidian.
Field-hunting tip
Look in volcanic rhyolitic lava flows country — that is the host setting where obsidian typically forms. If you start seeing rhyolite, pumice, feldspar in float, you are in the right ground. Field specimens usually show a massive habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Nevada, New Mexico, California — start trip planning there.
Common questions
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Find obsidian on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
