Mineral

Agate

Chalcedony (Microcrystalline Quartz) - SiO2

Hardness of 6.5-7 on the Mohs scale. Colors vary widely, but this specimen is pale grey/white with translucent to opaque banding. Waxy luster. Microcrystalline structure with no cleavage.

Identified June 18, 2026More mineral →

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Physical properties

Hardness of 6.5-7 on the Mohs scale. Colors vary widely, but this specimen is pale grey/white with translucent to opaque banding. Waxy luster. Microcrystalline structure with no cleavage.

Formation & geological history

Forms primarily in volcanic and metamorphic rocks from silica-rich groundwater filling cavities or veins. Deposition occurs in layers, creating the characteristic banding.

Uses & applications

Commonly used in jewelry (as cabochons or pendants, note the drilled hole in this piece), decorative items, and lapidary arts. Historically used for hardstone carving.

Geological facts

Agate was named by Theophrastus, a Greek philosopher and naturalist, who discovered the stone along the shoreline of the river Achates in Sicily.

Field identification & locations

Identify by its waxy luster, hardness (scratches glass), and characteristic banded or moss-like inclusions. Found worldwide, with notable deposits in Brazil, Uruguay, and the USA.