metamorphic
Quartzite Pepple
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: light grey to brownish, Luster: vitreous to dull, Crystal structure: Trigonal (granulated), Cleavage: None (conchoidal fracture)
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Physical properties
Hardness: 7 (Mohs scale), Color: light grey to brownish, Luster: vitreous to dull, Crystal structure: Trigonal (granulated), Cleavage: None (conchoidal fracture)
Formation & geological history
Formed when quartz-rich sandstone is subjected to heat and pressure (metamorphism). Usually Proterozoic or Paleozoic in age. This specimen appears water-worn from glacial or river transport.
Uses & applications
Used as construction aggregate, railway ballast, and occasionally for decorative landscaping or historical tool making.
Geological facts
Quartzite is so tough that it often outlasts the original rock formations and gets redistributed across great distances via glacial activity, which is common in areas like Minnesota.
Field identification & locations
Identify by its high hardness (scratches glass) and its sugary, granular appearance that reveals individual quartz grains fused together.
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