metamorphic
Quartz-rich metamorphic rock, likely quartzite
Quartzite, composed predominantly of quartz (SiO₂), with dark biotite, amphibole, or iron-oxide inclusions
AI-generated identification · may be incorrectTypically very hard (Mohs 7), white to gray, granular and vitreous to sugary in luster; quartz grains are recrystallized and tightly interlocked, with little obvious cleavage. The dark patches may be mica, amphibole, or weathered mineral inclusions.
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Physical properties
Typically very hard (Mohs 7), white to gray, granular and vitreous to sugary in luster; quartz grains are recrystallized and tightly interlocked, with little obvious cleavage. The dark patches may be mica, amphibole, or weathered mineral inclusions.
Formation & geological history
Forms when quartz-rich sandstone is subjected to substantial heat and pressure, commonly during mountain building; its exact geological age cannot be determined from the image and may range from Precambrian to much younger.
Uses & applications
Used as crushed stone, aggregate, road material, architectural stone, countertops, and occasionally as a decorative or lapidary material. This rough specimen has modest collector value.
Geological facts
Quartzite commonly resists weathering and forms ridges or durable boulders. It differs from sandstone because individual grains are fused rather than loosely cemented.
Field identification & locations
Look for extreme hardness: it commonly scratches glass and does not readily crumble along bedding; a streak test is white. Common worldwide in metamorphic mountain belts, including the Appalachians, Rocky Mountains, India, Brazil, and Scandinavia.
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