metamorphic
Iron-stained quartz-rich rock, possibly jasper/quartzite
Quartz (SiO₂) with iron-oxide staining; likely ferruginous quartzite or jasper
AI-generated identification · may be incorrectAngular, granular specimen with gray-white and reddish-brown zones, dull to slightly vitreous luster, and no obvious cleavage. Quartz-rich material is typically Mohs 7, with specific gravity around 2.6; iron oxides produce the red coloration.
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Physical properties
Angular, granular specimen with gray-white and reddish-brown zones, dull to slightly vitreous luster, and no obvious cleavage. Quartz-rich material is typically Mohs 7, with specific gravity around 2.6; iron oxides produce the red coloration.
Formation & geological history
Likely formed from silica-rich sediment or vein material later metamorphosed or cemented, with later oxidation of iron-bearing minerals. The image cannot establish a geological age; ferruginous quartzite and jasper are plausible in the Precambrian rocks and glacial deposits of northeastern Minnesota.
Uses & applications
Used as aggregate, building stone, lapidary material, and inexpensive decorative or tumbled stone. This rough piece has little commercial value unless it displays exceptional pattern or translucency.
Geological facts
The dark areas may contain magnetite, hematite, or weathered mafic minerals; a magnet test could help distinguish magnetite-bearing material. The red zones are commonly hematite or goethite staining.
Field identification & locations
Likely identifiable by its very hard, gritty quartz-rich texture and inability to scratch with a steel knife; quartz should scratch glass. Common regional sources include glacial till and Precambrian bedrock around the Lake Superior region, but a photo alone cannot distinguish jasper from quartzite or iron-rich breccia.
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