sedimentary

Iron-stained quartz/chert pebble

Microcrystalline quartz (SiO₂) with iron-oxide minerals, chiefly goethite/limonite

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; gray to tan with ochre-yellow-brown staining, dull to waxy luster, cryptocrystalline structure, and no visible cleavage. The rounded, polished surface indicates natural water abrasion or tumbling.

Identified August 26, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely silicified sediment or chert formed when silica replaced or cemented sediment, later weathered and stained by oxidized iron-rich fluids. Its precise geological age cannot be determined from the photograph.

Uses & applications

Used mainly as a lapidary, decorative, or collecting material; attractive pieces may be polished into cabochons or ornaments, but this specimen has limited commercial use.

Geological facts

The yellow-brown coloration is produced by hydrated iron oxides rather than by the quartz itself. Chert can resemble jasper, but jasper is generally more opaque and strongly colored.

Field identification & locations

Identify by its very hard, non-cleavable, fine-grained texture and inability to scratch with a steel knife; quartz-rich material scratches glass. Common in gravel beds, sedimentary terrains, and weathered iron-bearing formations.