sedimentary

Agate

Silicon dioxide (Chalcedony), SiO2

Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture, and typically exhibits concentric color 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, conchoidal fracture, and typically exhibits concentric color banding.

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

Widely used in jewelry, ornamental carvings, decorative objects, and industrial bearings.

Agate is one of the most common materials used in the art of lapidary and was highly valued in ancient civilizations as a talisman.

Easily identified by its distinctive banded patterns and waxy luster; commonly found in volcanic rock cavities worldwide.

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