mineral

Brown chalcedony/agatic jasper nodule

Microcrystalline quartz (SiO₂), likely iron-stained chalcedony with included or weathered host material

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; brown, amber, gray, and cream coloration; waxy to dull luster; cryptocrystalline quartz with no visible cleavage and conchoidal fracture. The rough, opaque appearance may indicate jasper or iron-oxide staining rather than gem-grade agate.

Identified September 14, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, commonly with successive chalcedony layers and iron-oxide staining. The specimen’s precise geological age cannot be determined from the photograph; deposits range from Paleozoic to recent.

Uses & applications

Used as lapidary material for cabochons, beads, carvings, and polished specimens; unattractive pieces have little industrial value compared with bulk quartz.

Geological facts

Chalcedony and jasper are varieties of microcrystalline quartz; the boundary between opaque jasper and translucent chalcedony can be gradual. Cutting or wetting the surface may reveal banding or translucency.

Field identification & locations

Look for waxy texture, conchoidal fracture, hardness sufficient to scratch glass, and possible hidden banding when viewed against light. Common in volcanic terrains worldwide, including Oregon, Mexico, Brazil, India, and Madagascar.