metamorphic
Iron-stained quartzite or quartz-rich metamorphic rock
Quartzite, predominantly crystalline SiO₂, with iron-oxide minerals (hematite/goethite)
AI-generated identification · may be incorrectTypically Mohs 7; tan, orange, red, and gray coloration with earthy to slightly vitreous luster. Interlocking quartz grains, massive texture, and little visible cleavage; iron staining produces the rusty patches.
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Physical properties
Typically Mohs 7; tan, orange, red, and gray coloration with earthy to slightly vitreous luster. Interlocking quartz grains, massive texture, and little visible cleavage; iron staining produces the rusty patches.
Formation & geological history
Formed when quartz-rich sandstone recrystallized under heat and pressure, likely during regional metamorphism; the exact geological age cannot be determined from the photograph. Surface oxidation of iron-bearing impurities created the orange-red coloration.
Uses & applications
Used as crushed stone, aggregate, paving, landscaping rock, and durable building stone; attractive pieces may be polished or sold as specimens. It is generally not gem-grade.
Geological facts
Quartzite commonly breaks across grains rather than around them and is harder than ordinary sandstone. A steel scratch test should fail to scratch fresh quartz surfaces, while the rock may scratch glass.
Field identification & locations
Common in metamorphic mountain belts worldwide, including the Appalachian, Rocky, Rocky Mountain, and Precambrian shield regions. Confirm by testing hardness and looking for fused quartz grains; a photo cannot exclude iron-rich sandstone or altered rock.
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