Black opal is the most prized variety of opal, characterized by its dark body tone which provides a dramatic contrast for its vibrant internal play-of-color. It is typically found in sedimentary deposits where silica-rich fluids have filled fissures in iron-rich rock, most notably in the Lightning Ridge fields of Australia. Collectors look for high-intensity flashes of red, orange, and green colors against a dark, saturated background.
Is this black 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 black opal with a known reference. Black 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. Black Opal leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Black Opal typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: black, dark gray.
- 5Look at form & habitCrystal system: amorphous. Typical habit: massive, nodular, or cavity filling.
Often confused with
Black Opal vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside black opal
Minerals reported to co-occur with black 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
- 1.98-2.20 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Amorphous
- Crystal habit
- Massive, Nodular, Or Cavity Filling
- Cleavage
- None
- Rarity
- Rare
- Uses
- Gemstone, Jewelry, Collector
- Host rock
- Sedimentary Ironstone or Claystone Layers
- Typical price
- $100-5000+ per carat depending on play-of-color and body tone
Where rockhounds find black opal
3 mapped spotsClassic worldwide localities
- Lightning Ridge, Australia
- Mintabie, Australia
- Ethiopia
Field-hunting tip
Look in sedimentary ironstone or claystone layers country — that is the host setting where black opal typically forms. If you start seeing quartz, ironstone, kaolinite in float, you are in the right ground. Field specimens usually show a massive, nodular, or cavity filling habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Nevada — start trip planning there.
Common questions
How do you identify black opal?+
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Can I find black opal in the United States?+
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Find black opal on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
