mineral

Agate (specifically Carnelian Agate or Sardagate)

Silicon dioxide (SiO2) - variety of chalcedony

AI-generated identification · may be incorrect

Hardness: 6.5–7 (Mohs scale); Color: Orange, red, reddish-brown, and white concentric bands; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline/cryptocrystalline); Cleavage: None; Specific gravity: 2.58–2.64

Hardness: 6
Color: Orange, red, reddish-brown, and white concentric bands
Luster: Waxy to vitreous

Identified March 15, 2026More mineral →

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Physical properties

Formation & geological history

Formed in gas cavities (vesicles) of volcanic rocks (basalts/andesites) where silica-rich fluids deposit layers over time. The red/orange hue comes from iron oxide impurities. Most specimens are from the Phanerozoic eon.

Uses & applications

Used primarily in jewelry (cabochons), lapidary arts, decorative items (coasters, bookends), and historically for cylinder seals and amulets.

Geological facts

The name 'Carnelian' comes from the Latin word 'carne' meaning flesh, due to its reddish tint. Agates have been used by humans as gemstones for over 3,000 years, with the famous 'Lake Superior Agate' being highly sought after in North America.

Field identification & locations

Identify in the field by looking for a waxy luster, translucent edges when held to light, and distinct concentric banding. Common locations include Brazil, Uruguay, India, and the Lake Superior region of the USA.