metamorphic
Quartz-rich sandstone or quartzite
Quartzite; predominantly crystalline SiO₂, possibly with feldspar and iron-oxide staining
AI-generated identification · may be incorrectTypically very hard (Mohs 7), gray to cream, with a sugary granular texture and vitreous to dull luster. The specimen appears fine- to medium-grained, massive, and strongly quartz-rich; exact cleavage is absent, with irregular fracture.
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Physical properties
Typically very hard (Mohs 7), gray to cream, with a sugary granular texture and vitreous to dull luster. The specimen appears fine- to medium-grained, massive, and strongly quartz-rich; exact cleavage is absent, with irregular fracture.
Formation & geological history
Likely began as quartz sandstone and was compacted and recrystallized during regional metamorphism, commonly during mountain-building events; its precise geological age cannot be determined from the photograph. Cream and rusty areas may reflect weathering and iron oxides along fractures.
Uses & applications
Used as crushed stone, aggregate, road material, dimension stone, and decorative rock; attractive pieces may be collected but this specimen does not appear gem-grade.
Geological facts
Quartzite commonly breaks across grains rather than around them, making fresh surfaces sparkle and resist scratching. It can resemble hard sandstone, but quartzite is generally tougher and more fused.
Field identification & locations
Common in metamorphic terrains worldwide, including the Appalachians, Rocky Mountains, Alps, and many Precambrian shields. A steel file should struggle to scratch it; dilute acid should produce no reaction unless carbonate cement is present.
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