metamorphic
Glacial Quartzite Cobble
Meta-orthoquartzite (SiO2)
Hardness: 7 (Mohs scale), Color: dull brownish-red with internal pink/white quartz grains visible, Luster: dull to vitreous when chipped, Crystal structure: granular/sugary, Cleavage: none, SG: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: dull brownish-red with internal pink/white quartz grains visible, Luster: dull to vitreous when chipped, Crystal structure: granular/sugary, Cleavage: none, SG: 2.65
Formation & geological history
Originally deposited as quartz-rich sandstone, this rock underwent high heat and pressure until the sand grains fused. It was likely transported and rounded by glacial movement during the Pleistocene era.
Uses & applications
Primarily used as construction aggregate, railway ballast, and decorative garden stone. Highly durable material for landscaping.
Geological facts
Quartzite is so strong that when it breaks, it fractures through the sand grains rather than around them. This specimen shows a 'weathering rind' or iron staining on its exterior surface.
Field identification & locations
Found in glacial till, riverbeds, and moraines across the Northern Hemisphere. To identify in the field, check for extreme hardness (scratches glass) and a sugary texture on fresh surfaces.
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