Fire opal is a transparent to translucent variety of opal known for its vibrant yellow, orange, or red body color. Unlike precious opal, it is often valued for its intense base color rather than play-of-color, and is typically found filling cavities within volcanic rhyolite rocks.
Is this fire 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 fire opal with a known reference. Fire 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. Fire Opal leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Fire Opal typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: red, orange, yellow.
- 5Look at form & habitCrystal system: amorphous. Typical habit: massive, reniform, botryoidal.
Often confused with
Fire Opal vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside fire opal
Minerals reported to co-occur with fire 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
- Transparent
- Crystal system
- Amorphous
- Crystal habit
- Massive, Reniform, Botryoidal
- Cleavage
- None
- Fluorescence
- Often Green to White Under LW UV
- Rarity
- Uncommon
- Uses
- Gemstone, Lapidary, Collector
- Host rock
- Volcanic Rhyolite Flows
- Typical price
- $20-200 per gram for rough, $100-2000 per carat for faceted gems
Where rockhounds find fire opal
17 mapped spotsClassic worldwide localities
- Querétaro, Mexico
- Hidalgo, Mexico
- Oregon, USA
- Ethiopia
U.S. states with fire opal
Each link opens a state-specific list of mapped rockhounding spots that produce fire opal.
Field-hunting tip
Look in volcanic rhyolite flows country — that is the host setting where fire opal typically forms. If you start seeing rhyolite, chalcedony, quartz in float, you are in the right ground. Field specimens usually show a massive, reniform, botryoidal habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in New Jersey, Nevada, Idaho — start trip planning there.
Common questions
How do you identify fire opal?+
Where is fire opal found?+
Can I find fire opal in the United States?+
How much is fire opal worth?+
What rocks look like fire opal?+
What minerals are found with fire opal?+
What kind of rock does fire opal form in?+
What is fire opal used for?+
Find fire opal on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
