Siliceous Oolite is a sedimentary rock composed of small, spherical grains called ooids that have been replaced by silica. Collectors look for the distinct 'fish egg' or 'ball-bearing' texture in a chert or chalcedony matrix, which polishes beautifully for lapidary work.
Is this siliceous oolite?
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 siliceous oolite with a known reference. Siliceous Oolite 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. Siliceous Oolite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Siliceous Oolite typically shows a waxy luster.
- 4Match the color rangeCompare against the expected color range: white, gray, tan, brown.
- 5Look at form & habitTypical habit: oolitic.
Often confused with
Siliceous Oolite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside siliceous oolite
Minerals reported to co-occur with siliceous oolite. 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
- 2.6-2.65 g/cm³
- Streak
- White
- Luster
- Waxy
- Transparency
- Opaque
- Crystal habit
- Oolitic
- Cleavage
- None
- Rarity
- Common
- Uses
- Lapidary, Collector, Decorative
- Host rock
- Sedimentary Layers
- Typical price
- $5-50 specimens
Where rockhounds find siliceous oolite
1 mapped spotsClassic worldwide localities
- Pennsylvania
- Missouri
- United Kingdom
- France
Field-hunting tip
Look in sedimentary layers country, the host setting where siliceous oolite typically forms. If you start seeing quartz, calcite, chalcedony in float, you are in the right ground. Field specimens usually show a oolitic habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Georgia. Start trip planning there.
More siliceous oolite photos
Common questions
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Find siliceous oolite on the map
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