sedimentary

Agate

Silicon dioxide (Chalcedony), SiO2

Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, microcrystalline crystal structure, and exhibits distinctive colored banding.

Identified November 14, 2026More sedimentary →

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Physical properties

Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, microcrystalline crystal structure, and exhibits distinctive colored banding.

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

Widely used for making ornamental objects, jewelry, polished specimens, and precision instruments like mortars and pestles.

Agate was highly prized in ancient civilizations like Egypt and Greece for use in amulets, seals, and ornate vessels.

Identified easily by its translucent nature, curved concentric color bands, and conchoidal fracture. Found worldwide 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