Sweetwater Agate is a translucent, nodular form of chalcedony found primarily in the gravel beds of Wyoming. Collectors highly prize these nodules for their distinctive yellow-green fluorescence under shortwave ultraviolet light caused by traces of uranium within the silica matrix.
Is this sweetwater agate?
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 sweetwater agate with a known reference. Sweetwater Agate 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. Sweetwater Agate leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Sweetwater Agate typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: clear, white, gray, tan, brown.
- 5Look at form & habitCrystal system: trigonal. Typical habit: nodular.
Often confused with
Sweetwater Agate vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside sweetwater agate
Minerals reported to co-occur with sweetwater agate. 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
- 2.60-2.65 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Nodular
- Cleavage
- None
- Fluorescence
- Often Fluoresces Yellow-green Under SW UV Due to Uranium Inclusions
- Rarity
- Common
- Uses
- Lapidary, Collector, Decorative
- Host rock
- Sedimentary Gravels and Volcanic Tuff
- Typical price
- $5-50 for small nodules, $50-200 for high-quality specimens
Where rockhounds find sweetwater agate
3 mapped spotsClassic worldwide localities
- Sweetwater County, Wyoming
- Fremont County, Wyoming
- Great Divide Basin, Wyoming
Field-hunting tip
Look in sedimentary gravels and volcanic tuff country, the host setting where sweetwater agate typically forms. If you start seeing quartz, calcite, fluorite in float, you are in the right ground. Field specimens usually show a nodular habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Wyoming. Start trip planning there.
More sweetwater agate photos
Common questions
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Find sweetwater agate on the map
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