metamorphic
Weathered quartz-rich rock, likely quartzite
Quartzite; predominantly crystalline SiO₂ with minor iron-oxide staining
AI-generated identification · may be incorrectTypically Mohs hardness 7, white to pale gray with rusty orange-brown surface staining, and a glassy to dull luster. Quartzite is massive and nonfoliated, lacks cleavage, and commonly has irregular fractures; the visible specimen may also contain weathered feldspar or silica-rich cement.
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Physical properties
Typically Mohs hardness 7, white to pale gray with rusty orange-brown surface staining, and a glassy to dull luster. Quartzite is massive and nonfoliated, lacks cleavage, and commonly has irregular fractures; the visible specimen may also contain weathered feldspar or silica-rich cement.
Formation & geological history
Forms when quartz-rich sandstone is recrystallized during regional or contact metamorphism, usually deep in the crust; its precise age cannot be determined from the image. Iron-bearing fluids or weathering produced the orange staining and surface alteration.
Uses & applications
Crushed quartzite is used for aggregate, road stone, and silica products; durable attractive pieces are used as building stone and occasionally as lapidary material. This rough specimen has little commercial value unless its locality or texture is unusual.
Geological facts
Quartzite commonly breaks across quartz grains rather than around them, unlike weakly cemented sandstone. It can resemble massive quartz, chert, or weathered granite in hand specimens.
Field identification & locations
Look for a very hard, quartz-rich surface that scratches glass and does not fizz with dilute hydrochloric acid; a fresh broken surface should appear granular and sugary. Common occurrences include mountain belts and ancient sandstone formations worldwide.
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