mineral

Agate

Silicon Dioxide (SiO2)

Hardness: 6.5 - 7 on Mohs scale; Color: Banded appearance with shades of white, gray, and reddish-orange; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline/cryptocrystalline); Specific gravity: 2.58 - 2.64

Hardness: 6
Luster: Vitreous to waxy

Identified July 19, 2026More mineral →

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Physical properties

Formation & geological history

Formed primarily within cavities (geodes) of volcanic rocks or certain metamorphic rocks. Silica-rich groundwater percolates into these voids, depositing layers of microcrystalline quartz over thousands of years.

Uses & applications

Used extensively in jewelry as cabochons, for ornamental carvings, paperweights, and industrially for mortar and pestles due to its hardness and chemical resistance.

Geological facts

Agate was named by the Greek philosopher Theophrastus, who discovered the stone along the shore line of the river Achates in present-day Sicily. It has been used in jewelry since the Neolithic era.

Field identification & locations

Identify in the field by its waxy luster, conchoidal fracture, and characteristic banding. Often found in riverbeds, lake shores, and volcanic regions like the Lake Superior area or Brazil.