Wood opal is a type of petrified wood where the original organic cellular structure has been replaced by amorphous opal rather than quartz. It retains the fine details of the original tree growth rings and bark texture while displaying a smooth, glassy, or waxy luster.
Is this wood 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 wood opal with a known reference. Wood 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. Wood Opal leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Wood Opal typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: brown, tan, gray, white, yellow, red, black.
- 5Look at form & habitCrystal system: amorphous. Typical habit: pseudomorphous after wood.
Often confused with
Wood Opal vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Luster reads vitreous on Wood Opal and waxy on Agate.
How to tell apart: Luster reads vitreous on Wood Opal and waxy on Jasper.
How to tell apart: Luster reads vitreous on Wood Opal and waxy on Chalcedony.
Often found alongside wood opal
Minerals reported to co-occur with wood 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
- 2.0-2.2 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Opaque
- Crystal system
- Amorphous
- Crystal habit
- Pseudomorphous After Wood
- Cleavage
- None
- Rarity
- Common
- Uses
- Lapidary, Collector, Decorative
- Host rock
- Sedimentary Deposits with Volcanic Ash
- Typical price
- $5-50 for small specimens, $100-2000 for large polished slabs
Where rockhounds find wood opal
1 mapped spotsClassic worldwide localities
- Arizona, USA
- Madagascar
- Argentina
- Indonesia
- Egypt
Field-hunting tip
Look in sedimentary deposits with volcanic ash country — that is the host setting where wood opal typically forms. If you start seeing quartz, chalcedony, pyrite in float, you are in the right ground. Field specimens usually show a pseudomorphous after wood habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Oregon — start trip planning there.
Common questions
How do you identify wood opal?+
Where is wood opal found?+
Can I find wood opal in the United States?+
How much is wood opal worth?+
What rocks look like wood opal?+
What minerals are found with wood opal?+
What kind of rock does wood opal form in?+
What is wood opal used for?+
Find wood opal on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
