mineral

Agate

Silicon dioxide (SiO2) - variety Chalcedony

Hardness: 6.5-7 (Mohs scale); Color: Banded turquoise, white, cream, and brown; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.58–2.64

Hardness: 6
Color: Banded turquoise, white, cream, and brown
Luster: Waxy to vitreous

Identified May 3, 2026More mineral →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Banded turquoise, white, cream, and brown; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.58–2.64

Formation & geological history

Formed in cavities (vesicles) of volcanic rocks or ancient lavas through the deposition of silica from groundwater. The bands represent different stages of mineral precipitation.

Uses & applications

Used primarily in lapidary arts for jewelry, decorative carvings, coasters, and as collector gemstones. Historically used for making precision bearings and mortar and pestles.

Geological facts

Agate is named after the Achates River in Sicily where it was first discovered. The 'Turquoise' color in this specimen is often a result of trace impurities or occasionally enhanced by dyeing to highlight the natural banding.

Field identification & locations

Identify by its characteristic concentric or planar banding and waxy texture. Commonly found in Brazil, Uruguay, and the Lake Superior region of the USA. Look for nodules in weathered volcanic soil.