gemstone

Agate

SiO2 (Silicon dioxide, cryptocrystalline quartz variety chalcedony)

Hardness: 6.5 to 7 on the Mohs scale. Color: Brown, white, amber, and translucent banding. Luster: Waxy to vitreous. Crystal structure: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None. Specific gravity: 2.58 to 2.64.

Hardness: 6
Color: Brown, white, amber, and translucent banding
Luster: Waxy to vitreous

Identified August 4, 2026More gemstone →

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Physical properties

Formation & geological history

Agate typically forms in cavities of volcanic rocks (like basalt) or ancient lavas where silica-rich groundwater deposits microscopic quartz crystals in concentric layers over millions of years.

Uses & applications

Used extensively in jewelry, ornamental carvings, polished display specimens, precision instruments, and metaphysical healing.

Geological facts

Agate is named after the Achates River in Sicily, where stones were found in antiquity. The distinct banding reflects successive pulses of silica-rich solutions entering the cavity.

Field identification & locations

Easily identified by its distinctive translucent curved or concentric color bands and waxy luster. Found worldwide, with major deposits in Brazil, Uruguay, India, and the USA.

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