mineral
Iron-stained Quartzite / Agate
Silicon Dioxide with Iron Oxides (SiO2 + Fe2O3·nH2O)
Hardness: 6.5-7 on Mohs scale; Color: Honey-brown, amber, yellowish-orange to dark reddish-brown; Luster: Waxy to resinous when wet; Crystal Structure: Microcrystalline/Cryptocrystalline trigonal; Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Honey-brown, amber, yellowish-orange to dark reddish-brown
- Luster
- Waxy to resinous when wet
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Honey-brown, amber, yellowish-orange to dark reddish-brown; Luster: Waxy to resinous when wet; Crystal Structure: Microcrystalline/Cryptocrystalline trigonal; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through hydrothermal deposition or precipitation of silica-rich fluids in rock cavities, often contaminated with iron oxide minerals like goethite or hematite during crystallization.
Uses & applications
Used in lapidary work, cabochon cutting, landscape decoration, and by amateur rockhounds for tumbled stones.
Geological facts
The distinctive golden-brown to orange color is caused by trace amounts of iron oxides (rust) staining or penetrating the silica matrix, which can range from surface coating to deep internal coloration.
Field identification & locations
Look for a microcrystalline texture, translucent thin edges, conchoidal fracture patterns, and high hardness (scratches steel). Commonly found in river beds, gravel deposits, and glacial drift.
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