mineral

Agate

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Multi-colored with translucent white, brown, and reddish-orange banding; Luster: Waxy to vitreous; Crystal structure: Trigonal (Cryptocrystalline quartz); Cleavage: None; Specific Gravity: 2.58-2.64

Hardness: 6
Luster: Waxy to vitreous

Identified June 24, 2026More mineral →

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Physical properties

Formation & geological history

Formed primarily within cavities of volcanic and metamorphic rocks through the deposition of silica from groundwater. The distinct bands are caused by variations in the mineral impurities during the deposition process over thousands of years.

Uses & applications

Extensively used for jewelry (cabochons, beads), decorative carvings, precision scales due to its hardness, and as a popular semi-precious gemstone for collectors.

Geological facts

Agate was named by the Greek philosopher Theophrastus, who discovered the stone along the shore line of the river Achates in Sicily. No two agates are exactly alike, as each one captures a unique chemical 'fingerprint' of its formation environment.

Field identification & locations

Identify in the field by looking for a waxy luster, conchoidal fracture (curved breaks like glass), and characteristic banding. Often found in riverbeds or near volcanic basalt outcrops. Common in Brazil, India, and the United States (Lake Superior region).