Owyhee Thundereggs are distinct rhyolitic nodules containing colorful, often plume-like, chalcedony cores. They are highly sought after by lapidary enthusiasts for their intricate internal banding and famous blue-hued varieties found in the Owyhee region of the American Pacific Northwest.
Is this owyhee thunderegg?
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 owyhee thunderegg with a known reference. Owyhee Thunderegg sits at Mohs 6.5-7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Owyhee Thunderegg leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Owyhee Thunderegg typically shows a waxy to vitreous luster.
- 4Match the color rangeCompare against the expected color range: blue, purple, white, gray, brown.
- 5Look at form & habitCrystal system: trigonal. Typical habit: nodular, orbicular.
Often confused with
Owyhee Thunderegg vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads waxy to vitreous on Owyhee Thunderegg and waxy on Agate.
How to tell apart: Luster reads waxy to vitreous on Owyhee Thunderegg and waxy on Jasper.
How to tell apart: Luster reads waxy to vitreous on Owyhee Thunderegg and waxy on Chalcedony.
Often found alongside owyhee thunderegg
Minerals reported to co-occur with owyhee thunderegg. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SiO₂
- Mohs hardness
- 6.5-7
- Density
- 2.6-2.7 g/cm³
- Streak
- White
- Luster
- Waxy to Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Nodular, Orbicular
- Cleavage
- None
- Rarity
- Common
- Uses
- Lapidary, Collector, Decorative
- Host rock
- Rhyolitic Volcanic Rock
- Typical price
- $10-100 per specimen depending on size and internal pattern
Where rockhounds find owyhee thunderegg
Classic worldwide localities
- Malheur County, Oregon, USA
- Owyhee Mountains, Idaho, USA
Field-hunting tip
Look in rhyolitic volcanic rock country, the host setting where owyhee thunderegg typically forms. If you start seeing quartz, chalcedony, rhyolite in float, you are in the right ground. Field specimens usually show a nodular, orbicular habit, so train your eye for that shape before scanning the outcrop.
More owyhee thunderegg photos
Common questions
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