sedimentary

Agate

Silicon Dioxide (Chalcedony), SiO2

Hardness of 6.5-7 on the Mohs scale, waxy luster, conchoidal fracture, and microscopic fibrous crystal structure.

Identified October 18, 2026More sedimentary →

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Physical properties

Hardness of 6.5-7 on the Mohs scale, waxy luster, conchoidal fracture, and microscopic fibrous crystal structure.

Forms by the deposition of silica from groundwater in cavities of igneous and sedimentary rocks over millions of years.

Widely used in jewelry, decorative ornaments, precision instruments, and lapidary art.

Agate is known for its distinct colorful bands and was prized in ancient civilizations for talismans and seals.

Identified by its waxy luster, hardness, and banded patterns; found globally in volcanic rock cavities.

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)