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.
- 2Name the organismDecide what left the fossil before worrying about the rock. Organism: Corals (class Anthozoa).
- 3Check the preservationPreservation: Calcium carbonate skeleton. That controls the weight, the hardness and how the piece takes a polish.
- 4Read the lusterHold the specimen under a strong light. Luster: dull to waxy.
- 5Match the color rangeCompare against the expected color range: white, brown, tan, gray, pink, yellow.
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
- Luster
- Dull to waxy
- Transparency
- Opaque
- Rarity
- Common
- Uses
- Lapidary, Collector, Decorative
- Host rock
- sedimentary strata
- Organism
- Corals (class Anthozoa)
- Preservation
- Calcium carbonate skeleton
Where rockhounds find calcified coral
3 mapped spotsClassic worldwide localities
- Florida, USA
- Indonesia
- Utah, USA
- Madagascar
- Canada
Field-hunting tip
Where it forms: sedimentary strata. If you start seeing calcite, quartz, dolomite in float, you are in the right ground. In the U.S., the densest reported localities are in Iowa. Start trip planning there.
More calcified coral photos
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.
