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, 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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Find black opal on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
