sedimentary

Agate

Silicon dioxide, SiO2

Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, microcrystalline quartz structure with distinctive color banding.

Identified October 28, 2026More sedimentary →

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Physical properties

Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, microcrystalline quartz structure with distinctive color banding.

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

Commonly used in jewelry, decorative ornaments, and precision instruments like mortars and pestles.

Agate bands often record environmental conditions during their formation, such as changes in water chemistry and temperature.

Easily identified by its translucent appearance and concentric or parallel color bands; 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

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)