mineral
Agate (Carnelian / Chalcedony)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 (Mohs scale); Color: Reddish-brown, translucent grey/white; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (Trigonal/Monoclinic); Cleavage: None; Fracture: Conchoidal.
- Hardness
- 6
- Color
- Reddish-brown, translucent grey/white
- Luster
- Waxy to vitreous
Identified More mineral →
Explore Agate (Carnelian / Chalcedony) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Reddish-brown, translucent grey/white; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (Trigonal/Monoclinic); Cleavage: None; Fracture: Conchoidal.
Formation & geological history
Formed as a secondary mineral in volcanic rock cavities (vugs) or sedimentary veins through the deposition of silica from groundwater. The red coloration is typically caused by iron oxide (hematite) inclusions.
Uses & applications
Used in gemstone jewelry, semi-precious carvings, ornamental stones, and historically for making burnishing tools or industrial mortars and pestles.
Geological facts
Agate is a variety of chalcedony. The reddish variety is specifically known as Carnelian. It has been used as a gemstone for over 4,500 years, notably by the ancient Egyptians and Sumerians for signet rings and amulets.
Field identification & locations
Identify in the field by its waxy luster when broken, translucent edges when held to light, and conchoidal (shell-like) fracture patterns. Frequently found in riverbeds or areas with weathered volcanic soil.
