sedimentary

Fossiliferous Limestone

Calcium carbonate with biological impressions (CaCO3)

Hardness of 3 on the Mohs scale, typically gray or tan, dull to earthy luster, with visible fossil fragments or impressions.

Identified October 21, 2026More sedimentary →

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Physical properties

Hardness of 3 on the Mohs scale, typically gray or tan, dull to earthy luster, with visible fossil fragments or impressions.

Formed from the accumulation and compaction of shell, coral, and algal debris in shallow marine environments over millions of years.

Used in construction, cement production, agriculture, and as educational fossil specimens.

Limestone often preserves ancient marine life, providing key insights into prehistoric aquatic ecosystems and Earth history.

Easily identified by its reaction to dilute hydrochloric acid and visible fossil fragments; commonly found in sedimentary rock formations worldwide.

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)