sedimentary

Agate

Silicon Dioxide (Chalcedony), SiO2

Hardness of 6.5 to 7 on the Mohs scale, exhibits translucent to opaque transparency with concentric color banding, and has a waxy to vitreous luster.

Identified October 18, 2026More sedimentary →

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Physical properties

Hardness of 6.5 to 7 on the Mohs scale, exhibits translucent to opaque transparency with concentric color banding, and has a waxy to vitreous luster.

Formed by the deposition of silica from groundwater in cavities of ancient volcanic and sedimentary rocks.

Widely used in ornamental carvings, jewelry making, and precision instruments like knife-edge bearings.

Agate bands represent successive layers of microscopic quartz crystals deposited over long geological periods.

Easily identified by distinctive concentric color rings and conchoidal fracture; commonly found worldwide in volcanic regions.

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

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Sandstone or Siltstone

Arenite (if sandstone)

Sandstone

Arenite

Shale

Shale (clastic sedimentary rock)

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)