Rock Identifier
Agate (Silicon Dioxide (Chalcedony), SiO2) — gemstone
gemstone

Agate

Silicon Dioxide (Chalcedony), SiO2

Hardness: 6.5 to 7 on the Mohs scale; Color: Variable, including white, gray, blue, red, green, yellow, brown; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline quartz); Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.60 to 2.65

Hardness
6
Luster
Vitreous to waxy
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Physical properties

Hardness: 6.5 to 7 on the Mohs scale; Color: Variable, including white, gray, blue, red, green, yellow, brown; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline quartz); Cleavage: None, exhibits conchoidal fracture; Specific gravity: 2.60 to 2.65

Formation & geological history

Formed mainly in cavities of volcanic and metamorphic rocks through the deposition of silica from groundwater solutions in concentric layers over long periods.

Uses & applications

Used for making ornamental objects, jewelry, decorative items, and precision instruments.

Geological facts

Agate is one of the most popular materials used in hardstone carving and was valued as a talisman in ancient civilizations.

Field identification & locations

Identified by its distinct banded appearance and waxy luster, commonly found worldwide in volcanic rock cavities and riverbeds.

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