sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness: 6.5 to 7 on the Mohs scale. Color: Variable, often banded with white, gray, blue, red, green, and brown. Luster: Waxy to vitreous. Crystal structure: Trigonal (microcrystalline quartz). Cleavage: None. Specific Gravity: 2.58 to 2.64.
- Hardness
- 6
- Luster
- Waxy to vitreous
Identified More sedimentary →
Explore Agate in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5 to 7 on the Mohs scale. Color: Variable, often banded with white, gray, blue, red, green, and brown. Luster: Waxy to vitreous. Crystal structure: Trigonal (microcrystalline quartz). Cleavage: None. Specific Gravity: 2.58 to 2.64.
Formation & geological history
Formed mainly by the deposition of silica from groundwater in the cavities of igneous and sedimentary rocks. Over millions of years, silica-rich solutions deposit microscopic quartz crystals in layers, creating the characteristic banding.
Uses & applications
Used primarily for ornamental objects, jewelry, decorative carvings, lapidary arts, and scientific instruments due to its durability.
Geological facts
Agate was named by Theophrastus, a Greek philosopher and naturalist, who discovered the stone along the shoreline of the Achates River in Sicily.
Field identification & locations
Identified by its waxy luster, conchoidal fracture, and distinctive concentric color bands. Commonly found in volcanic rock cavities worldwide, particularly in Brazil, Uruguay, India, and the western United States.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Quartz pebble
Silicon dioxide (SiO2)
sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Generic Pebble / Rock Fragment
Lithic fragment / Weathered rock
sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Banded Siltstone / Mudstone Pebble
Siltstone / Argillite
sedimentary