metamorphic
Weathered iron-stained quartzite or sandstone cobble
Quartzite, chiefly SiO₂, with iron-oxide staining; possibly ferruginous sandstone
AI-generated identification · may be incorrectHardness likely 6.5–7 if quartzite (about 5–6 if sandstone); tan, cream, and reddish-brown with dark iron-oxide patches, dull to slightly vitreous luster, and no obvious cleavage. The rounded shape and smooth surface indicate prolonged water or sediment abrasion.
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Physical properties
Hardness likely 6.5–7 if quartzite (about 5–6 if sandstone); tan, cream, and reddish-brown with dark iron-oxide patches, dull to slightly vitreous luster, and no obvious cleavage. The rounded shape and smooth surface indicate prolonged water or sediment abrasion.
Formation & geological history
Likely formed from quartz-rich sandstone that was compacted and, if quartzite, metamorphosed by heat and pressure; iron minerals later oxidized during weathering. Its exact geological age and locality cannot be determined from the photograph.
Uses & applications
Used mainly as a decorative or lapidary specimen, paperweight, or landscaping stone; quartzite is also used as aggregate and dimension stone. This example appears more collectible as an attractive hand specimen than as gem material.
Geological facts
The dark markings may be iron oxides, manganese oxides, weathered mineral veins, or surface staining rather than fossils. A glass-scratch test and inspection of a fresh fracture can distinguish quartzite from softer sandstone.
Field identification & locations
Common in river gravels and eroded quartz-rich terrains worldwide. Quartzite should scratch glass and resist a steel file; sandstone generally does not, and grains are more readily visible.
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