sedimentary
Agate
Silicon Dioxide (SiO2), microcrystalline variety of quartz
Hardness: 6.5-7 on the Mohs scale, Color: Varies widely (brown, red, yellow, grey, white), Luster: Vitreous to waxy, Crystal Structure: Trigonal (microcrystalline/cryptocrystalline), Cleavage: None, Specific Gravity: 2.60-2.65
- Hardness
- 6
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: 6.5-7 on the Mohs scale, Color: Varies widely (brown, red, yellow, grey, white), Luster: Vitreous to waxy, Crystal Structure: Trigonal (microcrystalline/cryptocrystalline), Cleavage: None, Specific Gravity: 2.60-2.65
Formation & geological history
Forms primarily within the cavities of volcanic and metamorphic rocks through the deposition of silica from groundwater in rhythmic layers over long geological periods.
Uses & applications
Used for ornamental objects, jewelry, lapidary art, mortars and pestles, and highly prized by rockhounds and mineral collectors.
Geological facts
Agate is one of the most popular stones used in lapidary work due to its durability and colorful banding patterns. It was named by Theophrastus, a Greek philosopher, who discovered the stone along the shore of the Achates river in Sicily.
Field identification & locations
Identified by its waxy luster, microcrystalline structure, and often conchoidal fracture. Commonly found in stream beds, gravel deposits, and volcanic regions worldwide.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Quartz pebble
Silicon dioxide (SiO2)
sedimentary
Generic Pebble / Rock Fragment
Lithic fragment / Weathered rock
sedimentary
Banded Siltstone / Mudstone Pebble
Siltstone / Argillite
sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary