Silicified oolite consists of spherical grains called ooids that have been replaced or cemented by microcrystalline silica. Collectors look for the distinct 'fish-egg' texture visible in cross-sections, which polishes beautifully for lapidary work.
Is this silicified 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 silicified oolite with a known reference. Silicified 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. Silicified Oolite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Silicified Oolite typically shows a waxy luster.
- 4Match the color rangeCompare against the expected color range: white, gray, brown, tan, red.
- 5Look at form & habitTypical habit: oolitic.
Often confused with
Silicified Oolite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside silicified oolite
Minerals reported to co-occur with silicified 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
- Translucent
- Crystal habit
- Oolitic
- Cleavage
- None
- Rarity
- Common
- Uses
- Lapidary, Collector, Decorative
- Host rock
- Sedimentary Basins
- Typical price
- $5-30 for small cabochons or rough specimens
Where rockhounds find silicified oolite
2 mapped spotsClassic worldwide localities
- Pennsylvania, USA
- Utah, USA
- France
- United Kingdom
Field-hunting tip
Look in sedimentary basins country, the host setting where silicified oolite typically forms. If you start seeing quartz, calcite, dolomite 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 silicified oolite photos
Common questions
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Find silicified oolite on the map
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