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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 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
Where rockhounds find sweetwater agate
3 mapped spotsClassic worldwide localities
- Sweetwater County, Wyoming
- Fremont County, Wyoming
- Great Divide Basin, Wyoming
Field-hunting tip
Where it forms: sedimentary gravels and volcanic tuff. If you start seeing quartz, calcite, fluorite in float, you are in the right ground. Typical habit: nodular. 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
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
