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 — that is 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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