sedimentary

Limestone (Crinoid Fossil Fragment)

Biogenic Calcite (CaCO3)

Hardness 3 on the Mohs scale, dull earthy luster, light grey to off-white color, effervesces vigorously in dilute acid.

Identified October 28, 2026More sedimentary →

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

Physical properties

Hardness 3 on the Mohs scale, dull earthy luster, light grey to off-white color, effervesces vigorously in dilute acid.

Formed in warm, shallow marine environments from the accumulation of calcium carbonate skeletal debris, often dating from the Paleozoic era.

Used in construction, lime production, cement manufacturing, and collected by amateur fossil hunters.

Crinoids, often called sea lilies, are marine animals related to starfish that have existed for hundreds of millions of years.

Identified by its columnar or cylindrical shape, calcite hardness, and reaction to mild acids. Found extensively in sedimentary limestone bedrock.

Fossil-bearing concretion, possibly containing a fossil shell or other organic inclusion

Calcareous concretion; exact fossil and host-rock composition are not identifiable from the image

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Sandstone or Siltstone

Arenite (if sandstone)

Sandstone

Arenite

Shale

Shale (clastic sedimentary rock)

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)