mineral

Banded Agate (Gray Agate)

Silicon Dioxide (SiO2) - Chalcedony

Hardness: 6.5-7 on Mohs scale; Color: Gray, white, and translucent; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.64.

Hardness: 6
Color: Gray, white, and translucent
Luster: Waxy to vitreous

Identified March 11, 2026More mineral →

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Physical properties

Formation & geological history

Formed in cavities (vesicles) of volcanic rocks (lava flows) or in certain types of metamorphic rocks. Silica-rich water deposits layers of chalcedony over time. These can range from millions of years old to relatively younger deposits.

Uses & applications

Used primarily for jewelry (cabochons), pocket stones, decorative carvings, and industrially for precision pendulums, mortars and pestles due to its hardness.

Geological facts

Agates get their name from the Achates River in Sicily. The banding represents rhythmic precipitation of silica. Unlike typical crystals, agate is microcrystalline, meaning its structure is so fine it can't be seen without a microscope.

Field identification & locations

Identify by observing the distinct parallel or concentric banding bands and its waxy surface. In the field, look in areas with volcanic history or riverbeds. For collectors, it is a sturdy, common, but beautiful entry-level gemstone.

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