Oolitic agates are distinctive chalcedony specimens featuring small, spherical ooids formed by concentric layers of silica around a nucleus. They are commonly found in sedimentary environments where they exhibit a textured, bead-like surface, often revealing complex patterns when polished for lapidary use.
Is this oolitic agates?
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 oolitic agates with a known reference. Oolitic Agates 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. Oolitic Agates leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Oolitic Agates typically shows a waxy luster.
- 4Match the color rangeCompare against the expected color range: white, gray, brown, tan, red.
- 5Look at form & habitCrystal system: trigonal. Typical habit: botryoidal.
Often confused with
Oolitic Agates vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside oolitic agates
Minerals reported to co-occur with oolitic agates. 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
- 2.65 g/cm³
- Streak
- White
- Luster
- Waxy
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Botryoidal
- Cleavage
- None
- Rarity
- Common
- Uses
- Lapidary, Collector, Decorative
- Host rock
- Sedimentary
- Typical price
- $5-50 for hand specimens
Where rockhounds find oolitic agates
1 mapped spotsClassic worldwide localities
- Wyoming
- Utah
- Montana
- Nevada
Field-hunting tip
Look in sedimentary country, the host setting where oolitic agates typically forms. If you start seeing calcite, dolomite, quartz in float, you are in the right ground. Field specimens usually show a botryoidal habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Iowa. Start trip planning there.
Common questions
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Find oolitic agates on the map
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