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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: waxy to vitreous.
- 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.
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
Where rockhounds find owyhee thunderegg
Classic worldwide localities
- Malheur County, Oregon, USA
- Owyhee Mountains, Idaho, USA
Field-hunting tip
Where it forms: rhyolitic volcanic rock. If you start seeing quartz, chalcedony, rhyolite in float, you are in the right ground. Typical habit: nodular, orbicular. Train your eye for that shape before scanning the outcrop.
More owyhee thunderegg photos
Common questions
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Find owyhee thunderegg on the map
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