metamorphic
Rounded quartz-rich pebble, likely quartzite
Quartzite; predominantly microcrystalline SiO₂
AI-generated identification · may be incorrectTypically Mohs hardness 7, white to gray with a dull-to-glassy luster, massive granular texture, and no obvious cleavage. The smooth shape and surface indicate stream or beach abrasion; small darker inclusions may be mica, iron oxides, or other minerals.
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Physical properties
Typically Mohs hardness 7, white to gray with a dull-to-glassy luster, massive granular texture, and no obvious cleavage. The smooth shape and surface indicate stream or beach abrasion; small darker inclusions may be mica, iron oxides, or other minerals.
Formation & geological history
Quartzite forms when quartz-rich sandstone is recrystallized under heat and pressure during metamorphism, commonly in Precambrian to younger mountain belts. This specimen was later weathered and rounded in a river, beach, or glacial environment.
Uses & applications
Quartzite is used as crushed stone, aggregate, road material, and durable building or facing stone; attractive varieties are polished or collected. This small pebble has modest commercial value.
Geological facts
Its grains are fused strongly enough that fractures commonly cut through quartz grains rather than around them. It can resemble quartz-rich granite or chert, but it generally lacks visible feldspar crystals or waxy conchoidal fracture.
Field identification & locations
Field identification: it should resist scratching by a steel knife and may scratch ordinary glass; a streak test is white. Common sources include mountain belts and quartzite-bearing river or glacial gravels worldwide.
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