Banded Opal is a variety of common opal that exhibits distinct, parallel color bands due to rhythmic deposition of silica-rich fluids. It lacks the characteristic play-of-color found in precious opal, but is highly prized by lapidary artists for its smooth texture and unique layering. It is typically found in volcanic cavities or as a replacement material in sedimentary rock environments.
Is this banded opal?
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 banded opal with a known reference. Banded Opal sits at Mohs 5.5-6.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: white, gray, brown, black, orange.
- 5Look at form & habitCrystal system: amorphous. Typical habit: botryoidal.
Often confused with
Banded Opal vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside banded opal
Minerals reported to co-occur with banded opal. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SiO₂·nH₂O
- Mohs hardness
- 5.5-6.5
- Density
- 1.9-2.2 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Amorphous
- Crystal habit
- Botryoidal
- Cleavage
- None
- Fluorescence
- Often green or white under UV
- Rarity
- Common
- Uses
- Lapidary, Collector, Decorative
- Host rock
- volcanic rhyolite, sedimentary claystones
Where rockhounds find banded opal
1 mapped spotsClassic worldwide localities
- Mexico
- Peru
- Australia
- USA
- Ethiopia
Field-hunting tip
Where it forms: volcanic rhyolite, sedimentary claystones. If you start seeing quartz, chalcedony, montmorillonite in float, you are in the right ground. Typical habit: botryoidal. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Idaho. Start trip planning there.
More banded opal photos
Common questions
How do you identify banded opal?+
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Find banded opal on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
