metamorphic
Weathered quartz-rich rock, possibly quartzite or silicified sandstone
Quartzite (predominantly microcrystalline quartz, SiO₂); precise identification requires testing
AI-generated identification · may be incorrectHardness about 7 Mohs, brown-gray to reddish coloration, dull to weakly vitreous luster, massive granular texture, and no obvious cleavage. The elongated shape and contrasting pale central zone may reflect bedding, veining, or weathering rather than crystal form.
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Physical properties
Hardness about 7 Mohs, brown-gray to reddish coloration, dull to weakly vitreous luster, massive granular texture, and no obvious cleavage. The elongated shape and contrasting pale central zone may reflect bedding, veining, or weathering rather than crystal form.
Formation & geological history
Likely formed when quartz-rich sandstone was compacted and recrystallized during metamorphism; alternatively, it may be strongly silicified sandstone. Age and provenance cannot be determined from the photograph.
Uses & applications
Quartzite is used as crushed stone, aggregate, road material, building stone, and occasionally as decorative or lapidary material; this weathered specimen has mainly collector value.
Geological facts
Quartzite commonly breaks across grains, producing irregular fractures, and is generally tougher than sandstone. The reddish-brown color typically comes from iron-oxide staining.
Field identification & locations
Look for grains fused into a hard surface, a glassy scratchable-by-quartz response, and little or no fizz with dilute hydrochloric acid. Common in metamorphic mountain belts worldwide; a streak, acid, and hardness test would help distinguish it from sandstone or chert.
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