sedimentary

Stromatolite

Biogenic sedimentary rock (Calcium carbonate / SiO2 replaced)

Hardness 3-7 depending on mineralization, banded or laminated internal structure, earthy to vitreous luster, brown to reddish-brown coloration.

Identified October 28, 2026More sedimentary →

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Physical properties

Hardness 3-7 depending on mineralization, banded or laminated internal structure, earthy to vitreous luster, brown to reddish-brown coloration.

Formed by the trapping, binding, and cementation of sedimentary grains by micro-organisms, notably cyanobacteria, dating back billions of years.

Used primarily as educational specimens, in decorative carvings, and by fossil collectors worldwide.

Stromatolites represent some of the oldest records of life on Earth, having played a crucial role in producing Earth's oxygen-rich atmosphere.

Identified by distinctive alternating light and dark wavy laminae; found in ancient marine and lacustrine sedimentary sequences globally.

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)