Calcified coral is a fossilized biological remain where the original calcium carbonate structure has been preserved or replaced by minerals. Collectors look for intricate, star-like patterns or honeycomb structures visible on cut and polished surfaces. It is often found in sedimentary layers that were once ancient marine environments.
Is this calcified coral?
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 calcified coral with a known reference. Calcified Coral sits at Mohs 3-4 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Calcified Coral leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Calcified Coral typically shows a dull to waxy luster.
- 4Match the color rangeCompare against the expected color range: white, brown, tan, gray, pink, yellow.
- 5Look at form & habitTypical habit: massive.
Often confused with
Calcified Coral vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Chalcedony is the harder of the two (Mohs 6.5-7 vs. 3-4); luster reads dull to waxy on Calcified Coral and waxy on Chalcedony.
How to tell apart: Agate is the harder of the two (Mohs 6.5-7 vs. 3-4); luster reads dull to waxy on Calcified Coral and waxy on Agate.
Often found alongside calcified coral
Minerals reported to co-occur with calcified coral. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Mohs hardness
- 3-4
- Density
- 2.6-2.7 g/cm³
- Streak
- White
- Luster
- Dull to Waxy
- Transparency
- Opaque
- Crystal habit
- Massive
- Cleavage
- None
- Rarity
- Common
- Uses
- Lapidary, Collector, Decorative
- Host rock
- Sedimentary Strata
- Typical price
- $5-50 for small specimens, up to $200 for large polished display pieces
Where rockhounds find calcified coral
3 mapped spotsClassic worldwide localities
- Florida, USA
- Indonesia
- Utah, USA
- Madagascar
- Canada
Field-hunting tip
Look in sedimentary strata country — that is the host setting where calcified coral typically forms. If you start seeing calcite, quartz, dolomite in float, you are in the right ground. Field specimens usually show a massive 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 calcified coral on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
