Rock Identifier
Fossilized coral or carbonate fossil fragment (Calcareous fossil, likely colonial coral (order Hexacorallia; uncertain from image)) — fossil
fossil

Fossilized coral or carbonate fossil fragment

Calcareous fossil, likely colonial coral (order Hexacorallia; uncertain from image)

AI-generated identification · may be incorrect

Pale white to tan, porous and irregular, enclosed in gray-green matrix; chiefly calcite/aragonite (CaCO₃), Mohs hardness about 3, dull to slightly waxy luster, with no obvious cleavage. The rounded, chambered/porous forms suggest fossil skeletal material rather than a crystalline mineral.

Identified More fossil →
Explore Fossilized coral or carbonate fossil fragment in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App StoreGoogle Play

Physical properties

Pale white to tan, porous and irregular, enclosed in gray-green matrix; chiefly calcite/aragonite (CaCO₃), Mohs hardness about 3, dull to slightly waxy luster, with no obvious cleavage. The rounded, chambered/porous forms suggest fossil skeletal material rather than a crystalline mineral.

Formation & geological history

Likely a marine carbonate fossil preserved by mineral replacement or cementation in limestone/mudstone; age cannot be determined from the image and may range from Paleozoic to Cenozoic.

Uses & applications

Primarily a teaching or collecting specimen; fossiliferous limestone may be used as aggregate, cement raw material, or ornamental stone, but this small specimen has no industrial use.

Geological facts

Acid testing with dilute hydrochloric acid or vinegar should produce visible fizz if carbonate is exposed, though coatings or silicification may suppress it.

Field identification & locations

Look for repeated corallite cups, honeycomb pores, or radial septa under magnification; common sources include marine limestone deposits worldwide. Avoid destructive testing and keep provenance information.

More like this

Other fossil specimens

Crinoid Stem Fossil in Matrix (Phylum Echinodermata, Class Crinoidea) — fossil

Crinoid Stem Fossil in Matrix

Phylum Echinodermata, Class Crinoidea

fossil
Chert with Fossil Brachiopod (Microcrystalline Quartz (SiO2) with Calcitic Brachiopod inclusion) — sedimentary

Chert with Fossil Brachiopod

Microcrystalline Quartz (SiO2) with Calcitic Brachiopod inclusion

sedimentary
Sedimentary Outcrop (Sandstone/Shale) (Sedimentary bedrock formation (variable composition)) — sedimentary

Sedimentary Outcrop (Sandstone/Shale)

Sedimentary bedrock formation (variable composition)

sedimentary
Crinoid Stem Fossils (Indian Beads / St. Cuthbert's Beads) (Crinoid columnal ossicles (phylum Echinodermata)) — fossil

Crinoid Stem Fossils (Indian Beads / St. Cuthbert's Beads)

Crinoid columnal ossicles (phylum Echinodermata)

fossil
Weathered fossiliferous sandstone or mudstone cobble (Lithified siliciclastic sediment; the raised curved feature may be a trace fossil or shell impression) — sedimentary

Weathered fossiliferous sandstone or mudstone cobble

Lithified siliciclastic sediment; the raised curved feature may be a trace fossil or shell impression

sedimentary
Weathered limestone or calcareous sandstone (Calcite-rich carbonate rock, chiefly calcium carbonate (CaCO₃), possibly fossiliferous limestone) — sedimentary

Weathered limestone or calcareous sandstone

Calcite-rich carbonate rock, chiefly calcium carbonate (CaCO₃), possibly fossiliferous limestone

sedimentary