metamorphic
Iron-rich quartzite or ironstone
Ferruginous quartzite; chiefly quartz (SiO₂) with iron oxides such as hematite and goethite
AI-generated identification · may be incorrectHardness about 6.5–7; rusty brown to dark gray, granular texture, and dull to slightly vitreous luster. Quartz has no cleavage, while iron oxides produce the mottled metallic-brown coloration; density is typically 2.7–3.5 g/cm³.
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Physical properties
Hardness about 6.5–7; rusty brown to dark gray, granular texture, and dull to slightly vitreous luster. Quartz has no cleavage, while iron oxides produce the mottled metallic-brown coloration; density is typically 2.7–3.5 g/cm³.
Formation & geological history
Likely formed when quartz-rich sandstone was metamorphosed and cemented or replaced by iron-bearing fluids, commonly during Precambrian geological periods. The photograph alone cannot establish an exact age or locality.
Uses & applications
Used locally as durable aggregate, road stone, and occasionally ornamental stone; iron-rich varieties may be collectible but are generally not gem material.
Geological facts
A strong streak of reddish-brown, moderate-to-strong attraction to a magnet, and a glassy quartz-rich fracture support ironstone identification. Some visually similar specimens are weathered iron ore or jasper.
Field identification & locations
Common in exposed, weathered terrains and iron-formation regions, including India, Australia, Brazil, and North America. Field identification requires a streak test, hardness test, magnet, and ideally thin-section or chemical analysis.
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