metamorphic
Iron-stained quartzite or quartz-rich rock
Quartz (SiO₂), likely in a quartzite matrix with iron-oxide/hydroxide coatings (hematite/goethite)
AI-generated identification · may be incorrectHardness about 7 Mohs; tan to rusty orange with a dull-to-glassy luster, granular texture, and no obvious cleavage. The rusty coloration likely comes from weathered iron minerals, while translucent gray-white areas suggest quartz.
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Physical properties
Hardness about 7 Mohs; tan to rusty orange with a dull-to-glassy luster, granular texture, and no obvious cleavage. The rusty coloration likely comes from weathered iron minerals, while translucent gray-white areas suggest quartz.
Formation & geological history
Likely formed when quartz-rich sandstone recrystallized during metamorphism, with later groundwater oxidation producing hematite/goethite staining; its exact geological age cannot be determined from the photograph.
Uses & applications
Primarily a geological or lapidary specimen; quartzite is used as aggregate, building stone, and occasionally decorative stone, while attractive iron-stained pieces may be tumbled or displayed.
Geological facts
Quartzite commonly breaks across quartz grains rather than around them and is typically harder than a steel knife. Orange-brown iron staining can develop long after the original rock formed.
Field identification & locations
Look for quartz grains fused into a hard mass, a scratch-resistant surface, and rusty coatings or fracture fillings; common in metamorphic terrains and stream gravels. A field hardness test and acid test would help distinguish it from iron-stained chert or sandstone.
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