metamorphic
Quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly quartz (SiO₂), with minor feldspar, mica, and iron-oxide staining
AI-generated identification · may be incorrectTypically very hard (Mohs 7), gray-white to tan, with a glassy to sugary luster and interlocking granular crystals; lacks obvious cleavage and commonly shows fractured, massive texture. The specimen’s weathered, mottled appearance makes exact identification uncertain from the image alone.
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Physical properties
Typically very hard (Mohs 7), gray-white to tan, with a glassy to sugary luster and interlocking granular crystals; lacks obvious cleavage and commonly shows fractured, massive texture. The specimen’s weathered, mottled appearance makes exact identification uncertain from the image alone.
Formation & geological history
Forms when quartz-rich sandstone is recrystallized under elevated heat and pressure during regional metamorphism, commonly during mountain building. Its age depends on the original sandstone and metamorphic event.
Uses & applications
Used as crushed stone, road aggregate, railroad ballast, and durable building or decorative stone; attractive pieces may be collected, though this example appears ordinary.
Geological facts
Quartzite is generally tougher than sandstone because its quartz grains are fused together. A steel knife typically will not scratch it, while quartzite can scratch ordinary glass.
Field identification & locations
Common in metamorphic mountain belts worldwide, including the Appalachians, Rocky Mountains, Alps, and Scandinavian mountains. Confirm by testing hardness and looking for fused quartz grains rather than visible sand grains or strong foliation.
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