sedimentary

Agate

Silicon dioxide (chalcedony, SiO2)

Hardness of 6.5-7 on the Mohs scale, waxy to vitreous luster, microcrystalline crystal structure, and conchoidal fracture.

Identified November 14, 2026More sedimentary →

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Physical properties

Hardness of 6.5-7 on the Mohs scale, waxy to vitreous luster, microcrystalline crystal structure, and conchoidal fracture.

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

Used primarily in lapidary arts, ornamental carvings, jewelry, and precision instruments like mortars and pestles.

Agate is a variety of chalcedony and often displays distinct concentric banding formed by successive layers of silica deposition.

Found worldwide in volcanic rock cavities; identified by its translucent appearance, banded patterns, and resistance to steel.

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