metamorphic
Weathered quartz-rich sandstone or quartzite
Quartzite (predominantly SiO₂), possibly strongly cemented sandstone
AI-generated identification · may be incorrectPale cream to tan, massive and fine-grained with a dull to slightly sugary luster; likely Mohs 6.5–7, with no obvious cleavage and conchoidal to irregular fracture. Exact identification requires a close grain view and a hardness test.
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Physical properties
Pale cream to tan, massive and fine-grained with a dull to slightly sugary luster; likely Mohs 6.5–7, with no obvious cleavage and conchoidal to irregular fracture. Exact identification requires a close grain view and a hardness test.
Formation & geological history
If quartzite, it formed when quartz sandstone was compacted and recrystallized during metamorphism, commonly during regional mountain-building; if sandstone, it is lithified sedimentary sand. Its age cannot be determined from the photograph.
Uses & applications
Used as crushed aggregate, road stone, building stone, and occasionally decorative material; attractive quartzite can be used for landscaping or slabs. This ordinary weathered specimen has little commercial value.
Geological facts
Quartz-rich rocks commonly resist weathering, leaving rounded, pale cobbles while softer surrounding minerals erode. A steel knife should not scratch quartzite, whereas calcite-rich rocks would fizz with dilute hydrochloric acid.
Field identification & locations
Common in regions with exposed sandstone formations or metamorphic belts, including the Appalachians, Rocky Mountains, and many glacial deposits. Look for visible sand grains and weak cement (sandstone) versus interlocking quartz grains and very hard fracture surfaces (quartzite).
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