sedimentary

Agate

Silicon Dioxide (Chalcedony), SiO2

Hardness of 6.5 to 7 on the Mohs scale, waxy luster, microcrystalline structure, and displays concentric banding of various colors.

Identified November 13, 2026More sedimentary →

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Physical properties

Hardness of 6.5 to 7 on the Mohs scale, waxy luster, microcrystalline structure, and displays concentric banding of various colors.

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

Widely used in ornamental carvings, jewelry, polished specimens, and precision laboratory instruments.

Agate was named by Theophrastus after the Achates River in Sicily where ancient specimens were found.

Identify by its waxy luster, conchoidal fracture, and distinct multicolored bands; 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

Sandstone or Siltstone

Arenite (if sandstone)

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Shale

Fissile Sedimentary Rock

Sandstone

Arenite

Shale

Clastic sedimentary rock