Coral fossils occur when ancient coral colonies are buried in sediment and replaced by silica-rich fluids over millions of years. Look for distinctive floral or honeycomb patterns on the surface that represent the original skeletal structure of the coral polyps. These specimens are highly prized by lapidaries for their intricate internal details and ability to take a high polish.

Hardness

6.5-7

Mohs

Luster

Waxy

Transparency

Translucent

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Coral Fossil

Hardness: 6.5-7
Luster: Waxy
Transparency: Translucent

Is this coral fossil?

4-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 coral fossil with a known reference. Coral Fossil sits at Mohs 6.5-7, softer than the next harder reference, harder than the previous one.
2
Name the organism
Decide what left the fossil before worrying about the rock. Organism: Corals (class Anthozoa).
3
Read the luster
Hold the specimen under a strong light. Luster: waxy.
4
Match the color range
Compare against the expected color range: white, tan, brown, red, orange, pink, gray.

Often confused with

Coral Fossil vs. its common look-alikes, and how to tell them apart in the field.

Often found alongside coral fossil

Minerals reported to co-occur with coral fossil. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Mohs hardness: 6.5-7
Density: 2.5-2.7 g/cm³
Colors: White Tan Brown Red Orange Pink Gray
Luster: Waxy
Transparency: Translucent
Rarity: Common
Uses: Lapidary, Collector, Decorative
Host rock: sedimentary
Organism: Corals (class Anthozoa)

Where rockhounds find coral fossil

Classic worldwide localities

Florida, USA
Georgia, USA
Indonesia
Hungary

Field-hunting tip

Where it forms: sedimentary. If you start seeing chalcedony, quartz, calcite in float, you are in the right ground.

Common questions

How do you identify coral fossil?+

Mohs hardness is 6.5-7. Organism: Corals (class Anthozoa). Luster: waxy. Common colors include white, tan, brown, red.

Where is coral fossil found?+

Notable localities include Florida, USA; Georgia, USA; Indonesia; Hungary.

What rocks look like coral fossil?+

Coral Fossil is most often confused with Chalcedony, Jasper, Agate. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with coral fossil?+

Coral Fossil commonly co-occurs with Chalcedony, Quartz, Calcite, Limestone. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does coral fossil form in?+

Where it forms: sedimentary. Working float back to the host body is the standard way to chase a fresh occurrence.

What is coral fossil used for?+

Coral Fossil is used in lapidary, collector, decorative.

Find coral fossil on the map

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