mineral

Yellow chalcedony (possibly iron-stained agate)

Microcrystalline quartz, SiO₂; yellow coloration likely from hydrated iron oxides

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; waxy to vitreous luster, white to honey-yellow color, translucent edges, conchoidal fracture, no cleavage, cryptocrystalline quartz structure; specific gravity about 2.6.

Identified August 24, 2026More mineral →

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Physical properties

Hardness 6.5–7 Mohs; waxy to vitreous luster, white to honey-yellow color, translucent edges, conchoidal fracture, no cleavage, cryptocrystalline quartz structure; specific gravity about 2.6.

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, commonly as chalcedony or agate; yellow staining develops from iron-bearing fluids. Usually Cenozoic to older volcanic-host-rock environments.

Uses & applications

Used as a lapidary material for cabochons, carvings, beads, and polished specimens; durable but less valuable than fine transparent gemstones.

Geological facts

The rounded, waxy appearance and lack of visible crystal faces are typical of chalcedony. Stronger yellow-orange zones may indicate limonite or goethite inclusions rather than naturally yellow quartz.

Field identification & locations

Identify with a waxy luster, conchoidal fracture, translucency, and scratch resistance against glass; acid does not usually react. Common in volcanic terrains and gravel beds worldwide, including Oregon, California, Brazil, India, and Madagascar.