metamorphic
Ferruginous Quartz (Agatized/Iron-stained Quartzite)
Silicon Dioxide (SiO2) with Iron Oxide (Fe2O3) inclusions
Hardness: 7 (Mohs scale), Color: Translucent white to orange/red/brown, Luster: Vitreous to waxy, Crystal Structure: Hexagonal/Trigonal, Cleavage: None/Conchoidal fracture, Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Translucent white to orange/red/brown, Luster: Vitreous to waxy, Crystal Structure: Hexagonal/Trigonal, Cleavage: None/Conchoidal fracture, Specific Gravity: 2.65
Formation & geological history
Formed from the metamorphism of quartz sandstone (quartzite) or precipitation of silica in volcanic cavities. Iron-rich groundwater seeped into the micro-cracks over millions of years (often during the Phanerozoic eon) to create the orange-red staining.
Uses & applications
Used primarily as decorative river stones, lapidary material for tumbling, and in some architectural aggregate. High-purity quartz is used in electronics, but stained specimens are purely for collecting and decor.
Geological facts
The orange color is caused by hematite or limonite staining. This specific specimen appears to be a 'river cobble,' meaning its smooth, rounded surface was sculpted by natural water erosion in a stream or beach over thousands of years.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and waxy translucency. Commonly found in riverbeds, glacial till, and coastal areas. Collectors look for 'vugs' or small crystalline pockets within the larger mass.
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