sedimentary

Agate

Silicon Dioxide (SiO2)

Hardness of 7 on Mohs scale, waxy to vitreous luster, translucent to opaque, with a microcrystalline quartz structure and no cleavage.

Identified November 13, 2026More sedimentary →

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Physical properties

Hardness of 7 on Mohs scale, waxy to vitreous luster, translucent to opaque, with a microcrystalline quartz structure and no cleavage.

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

Used in jewelry, decorative ornaments, gemstone carving, and precision laboratory instruments.

Agate is a variety of chalcedony and has been used by humans for ornamentation and seals since ancient Neolithic times.

Identified by its distinctive concentric banding and conchoidal fracture, commonly 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