Wood opal is a type of petrified wood where the original organic cellular structure has been replaced by amorphous opal rather than quartz.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.
- 2Name the organismDecide what left the fossil before worrying about the rock. Organism: Wood.
- 3Check the preservationPreservation: Cell walls replicated by silica in the form of opal. That controls the weight, the hardness and how the piece takes a polish.
- 4Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 5Match the color rangeCompare against the expected color range: brown, tan, gray, white, yellow, red, black.
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
- Mohs hardness
- 5.5-6.5
- Density
- 2.0-2.2 g/cm³
- Luster
- Vitreous
- Transparency
- Opaque
- Rarity
- Common
- Uses
- Lapidary, Collector, Decorative
- Host rock
- Sedimentary deposits with volcanic ash
- Organism
- Wood
- Preservation
- Cell walls replicated by silica in the form of opal
Where rockhounds find wood opal
1 mapped spotsClassic worldwide localities
- Arizona, USA
- Madagascar
- Argentina
- Indonesia
- Egypt
Field-hunting tip
Where it forms: Sedimentary deposits with volcanic ash. If you start seeing quartz, chalcedony, pyrite in float, you are in the right ground. In the U.S., the densest reported localities are in Oregon. Start trip planning there.
Common questions
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Find wood opal on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
