mineral

Agate

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Highly variable, showing concentric bands or moss-like patterns. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (hexagonal system). Cleavage: None. Specific gravity: 2.58-2.64.

Hardness: 6
Luster: Waxy to vitreous

Identified March 27, 2026More mineral →

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Physical properties

Formation & geological history

Formed as secondary deposits in cavities (vesicles) within volcanic rocks or certain metamorphic rocks. Silica-rich groundwater fills these voids over thousands of years, depositing layers of microcrystalline quartz. Found in strata ranging from Precambrian to Cenozoic ages.

Uses & applications

Commonly used in jewelry (cabochons, beads), decorative carvings, precision balances, mortars and pestles for chemical labs, and as highly sought-after collector pieces.

Geological facts

Agate is named after the Achates River (now Drillo) in Sicily. It was a prized gemstone in ancient Egypt and Mesopotamia for talismans. Many varieties exist, such as Fire Agate, Moss Agate, and Lace Agate.

Field identification & locations

Identify in the field by its waxy luster, translucency (hold to light), and characteristic banding. Often found in riverbeds, lake shores (like Lake Superior), and gravel deposits. Collectors look for unique banding patterns and vibrant colors.