Mineral

Agate

Cryptocrystalline quartz (SiO2)

Hardness 6.5-7 on Mohs scale, highly variable color often with banding, waxy to vitreous luster, cryptocrystalline structure, no cleavage, specific gravity 2.58-2.64

Identified June 19, 2026More mineral →

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Physical properties

Hardness 6.5-7 on Mohs scale, highly variable color often with banding, waxy to vitreous luster, cryptocrystalline structure, no cleavage, specific gravity 2.58-2.64

Formation & geological history

Formed primarily in volcanic and metamorphic rocks from silica-rich fluids filling cavities and cooling slowly over millions of years.

Uses & applications

Used extensively in jewelry, lapidary arts, ornamental objects, and historically for hardstone carving and some industrial grinding tools.

Geological facts

Agate is a variety of chalcedony characterized by its fineness of grain and brightness of color. It forms in concentric layers in a wide variety of colors and textures.

Field identification & locations

Identified by its distinctive banding, waxy luster, and high hardness. Commonly found worldwide in areas with historic volcanic activity. Collectors look for unique patterns and vibrant, contrasting colors.