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Siliceous Oolite is a sedimentary rock composed of small, spherical grains called ooids that have been replaced by silica.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.

Hardness
6.5-7
Mohs
Luster
Waxy
Streak
White
Transparency
Opaque

Is this siliceous oolite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

  • 1
    Test the hardness
    Try 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.
  • 2
    Check the streak
    Drag the specimen across an unglazed porcelain plate. Siliceous Oolite leaves a white streak.
  • 3
    Read the luster
    Hold the specimen under a strong light. Siliceous Oolite typically shows a waxy luster.
  • 4
    Match the color range
    Compare against the expected color range: white, gray, tan, brown.
  • 5
    Look at form & habit
    Typical habit: oolitic.

Often confused with

Siliceous Oolite vs. its common look-alikes — and how to tell them apart in the field.

Oolitic Limestone sedimentary
sedimentary
Oolitic Limestone
Mohs 3

How to tell apart: Siliceous Oolite is noticeably harder (Mohs 6.5-7 vs. 3); luster reads waxy on Siliceous Oolite and dull on Oolitic Limestone.

Compare →

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
Colors
WhiteGrayTanBrown
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 spots

Classic worldwide localities

  • Pennsylvania
  • Missouri
  • United Kingdom
  • France

Field-hunting tip

Look in sedimentary layers country — that is 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.

Browse 1 U.S. spots for siliceous oolite →

Common questions

How do you identify siliceous oolite?+
Mohs hardness is 6.5-7. It typically shows a waxy luster. The streak is white. Common colors include white, gray, tan, brown.
Where is siliceous oolite found?+
Notable localities include Pennsylvania; Missouri; United Kingdom; France.
Can I find siliceous oolite in the United States?+
RockHoundR maps 1 siliceous oolite rockhounding spots across 1 U.S. states — the top states are Georgia.
How much is siliceous oolite worth?+
Typical asking prices fall in the range of $5-50 specimens. Quality, size, and provenance can move individual specimens well outside that range.
What rocks look like siliceous oolite?+
Siliceous Oolite is most often confused with Oolitic Limestone. A quick hardness test and a streak check separate the look-alikes faster than color alone.
What minerals are found with siliceous oolite?+
Siliceous Oolite commonly co-occurs with Quartz, Calcite, Chalcedony. Spotting any of these in float or country rock is a useful trip signal.
What kind of rock does siliceous oolite form in?+
Siliceous Oolite typically forms in sedimentary layers. Working float back to the host body is the standard way to chase a fresh occurrence.
What is siliceous oolite used for?+
Siliceous Oolite is used in lapidary, collector, decorative.

Find siliceous oolite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.

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