sedimentary

Agate

Silicon dioxide (Chalcedony, SiO2)

Hardness of 6.5 to 7 on the Mohs scale, waxy luster, conchoidal fracture, and distinct parallel color banding.

Identified October 28, 2026More sedimentary →

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Physical properties

Hardness of 6.5 to 7 on the Mohs scale, waxy luster, conchoidal fracture, and distinct parallel color banding.

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

Widely used in jewelry, decorative ornaments, precision instruments, and gemstone collecting.

Agate is a microcrystalline variety of quartz and was highly prized in ancient civilizations for talismans and seal rings.

Identify by its translucent bands of color and hardness that scratches glass; 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)