Rock Identifier
Yellow Agate (Chalcedony (cryptocrystalline silica), SiO2) — mineral
mineral

Yellow Agate

Chalcedony (cryptocrystalline silica), SiO2

Hardness: 6.5–7 on Mohs scale; Color: Honey-yellow, golden-brown with white creamy bands; Luster: Waxy to vitreous; Crystal structure: Trigonal/Monoclinic (Microscopic); Cleavage: None; Specific gravity: 2.58–2.64.

Hardness
6
Color
Honey-yellow, golden-brown with white creamy bands
Luster
Waxy to vitreous
Identified More mineral

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Physical properties

Hardness: 6.5–7 on Mohs scale; Color: Honey-yellow, golden-brown with white creamy bands; Luster: Waxy to vitreous; Crystal structure: Trigonal/Monoclinic (Microscopic); Cleavage: None; Specific gravity: 2.58–2.64.

Formation & geological history

Formed primarily in volcanic rock cavities (vesicles) from silica-rich groundwater over millenia. The bands represent different pulses of mineral-rich fluids depositing layers on the cavity walls.

Uses & applications

Used in gemstone jewelry (cabochons, pendants), decorative carvings, metaphysical stones, and historically for precision tools or mechanical seals due to its hardness.

Geological facts

Agate is named after the Achates River in Sicily where it was first discovered. In ancient cultures, yellow agate was often associated with solar energy and thought to provide protection and courage to the wearer.

Field identification & locations

Identify in the field by its distinct concentric banding, waxy surface when broken, and lack of cleavage. Common in Brazil, India, and the Midwestern United States (Lake Superior region). It cannot be scratched by a steel knife.