sedimentary

Agate

Silicon dioxide (Chalcedony, SiO2)

Hardness of 6.5-7 on the Mohs scale, waxy to vitreous luster, microcrystalline crystal structure, and distinct concentric banding in various colors.

Identified October 24, 2026More sedimentary →

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Physical properties

Hardness of 6.5-7 on the Mohs scale, waxy to vitreous luster, microcrystalline crystal structure, and distinct concentric banding in various colors.

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

Widely used in jewelry, decorative ornaments, ornate carvings, and precision instruments like mortars and pestles.

Agate is a variety of chalcedony and was historically used by ancient civilizations for amulets, seals, and weaponry like arrowheads.

Easily identified by its characteristic translucent banding 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

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)