sedimentary

Agate

Silicon dioxide (chalcedony), SiO2

Hardness of 6.5 to 7 on the Mohs scale, waxy luster, and conchoidal fracture. Displays distinct multicolored bands or concentric layers.

Identified November 14, 2026More sedimentary →

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Physical properties

Hardness of 6.5 to 7 on the Mohs scale, waxy luster, and conchoidal fracture. Displays distinct multicolored bands or concentric layers.

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

Commonly used in jewelry, ornamental carvings, decorative objects, and as a collector's specimen.

Agate was highly prized by ancient civilizations like the Greeks and Egyptians for making seals, rings, and healing talismans.

Identify by its waxy luster, distinct banding patterns, and ability to scratch glass. 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