sedimentary

Agate

Silicon Dioxide (SiO2)

Hardness of 6.5-7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure with distinct colorful banding, and conchoidal fracture.

Identified October 18, 2026More sedimentary →

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Physical properties

Hardness of 6.5-7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure with distinct colorful banding, and conchoidal fracture.

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

Widely used in ornamental jewelry, decorative carvings, lapidary arts, and precision instruments.

Agates are often found lining or filling geodes and have been used as gemstones and talismans since antiquity.

Easily identified by concentric bands of varying color and translucency; commonly found in riverbeds and 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)