metamorphic
Quartz-rich iron-stained metamorphic rock (likely quartzite)
Quartzite; predominantly quartz (SiO₂) with iron oxides/hydroxides, possibly feldspar and mica
AI-generated identification · may be incorrectHardness about 7 Mohs; pale gray to tan with rusty orange-brown staining, granular texture, and vitreous to dull luster. Quartz has no cleavage and commonly forms interlocking grains; the specimen appears dense and fractured.
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Physical properties
Hardness about 7 Mohs; pale gray to tan with rusty orange-brown staining, granular texture, and vitreous to dull luster. Quartz has no cleavage and commonly forms interlocking grains; the specimen appears dense and fractured.
Formation & geological history
Forms when quartz-rich sandstone is recrystallized during regional or contact metamorphism, typically during mountain building; its exact geological age cannot be determined from the image. Rust colors result from weathering of iron-bearing minerals.
Uses & applications
Used as crushed stone, aggregate, road material, dimension stone, and occasionally decorative material; attractive pieces may be collected but are generally low-value.
Geological facts
Quartzite commonly breaks across grains rather than around them, producing very sharp, irregular fractures. Iron staining may occur along fractures and weathered surfaces.
Field identification & locations
Likely identification: scratches glass and steel, lacks obvious flat cleavage surfaces, and is harder than ordinary sandstone; a streak, acid, and close examination of grain boundaries would help confirm it. Common in metamorphic mountain belts worldwide.
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