sedimentary (secondary classification for a weathered mineral specimen)

Ferruginous Quartz (River Pebble)

Silicon Dioxide (SiO2) with Iron Oxide inclusions

Hardness: 7 on Mohs scale; Color: Reddish-brown, tan, or rusty orange; Luster: Vitreous to dull (weathered); Crystal structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Reddish-brown, tan, or rusty orange
Luster: Vitreous to dull (weathered)

Identified March 14, 2026More sedimentary (secondary classification for a weathered mineral specimen) →

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Physical properties

Formation & geological history

Formed through hydrothermal processes then weathered and transported via river systems. Oxidation of iron minerals gives it the rusty hue. Found in alluvial deposits within ancient riverbeds or modern floodplains.

Uses & applications

Common industrial use in gravel and construction aggregate; low-grade lapidary use for tumbling; minimal value beyond decorative landscape stone.

Geological facts

Quartz is one of the most abundant minerals on Earth. The 'rusty' coating on this specimen is likely limonite or hematite staining, which occurs when iron-rich water interacts with the silica structure over thousands of years.

Field identification & locations

Identify in the field by its hardness (it can scratch glass) and its rounded, water-worn edges. Common in almost all temperate and tropical river basins globally. Collectors look for pieces with high translucency or 'ghost' inclusions.

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Agate (Chert/Chalcedony)

Silicon Dioxide (SiO2)

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Botryoidal Hematite (included in Quartz/Limonite matrix)

Fe2O3 (Hematite) on Quartz (SiO2) / Limonite

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Quartz Pebble (likely Chalcedony or Quartzite)

Silicon Dioxide (SiO2)

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