metamorphic
Banded Quartzite Cobble
Quartzite (SiO2 with minor iron oxides)
Hardness: 7 on Mohs scale. Color: Tan, beige, pinkish-orange, and grayish-blue layers. Luster: Vitreous to dull/earthy when weathered. Structure: Granoblastic texture, non-foliated to weakly layered metamorphism. Cleavage: None (conchoidal to uneven fracture).
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, pinkish-orange, and grayish-blue layers
- Luster
- Vitreous to dull/earthy when weathered
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Physical properties
Hardness: 7 on Mohs scale. Color: Tan, beige, pinkish-orange, and grayish-blue layers. Luster: Vitreous to dull/earthy when weathered. Structure: Granoblastic texture, non-foliated to weakly layered metamorphism. Cleavage: None (conchoidal to uneven fracture).
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone under high pressure and temperature, recrystallizing quartz grains. The distinct coloration is due to iron oxides and trace minerals. Later rounded and smoothed by stream or glacial erosion.
Uses & applications
Used as construction aggregate, decorative landscaping stone, and occasionally for lapidary work or tumbled stones.
Geological facts
Quartzite is extremely durable and resistant to both chemical and physical weathering, often surviving long transport distances in rivers and glacial till.
Field identification & locations
Identify in the field by its extreme hardness (scratches glass easily), sugary recrystallized quartz appearance, and smooth, rounded water-worn cobble shape. Commonly found in riverbeds, glacial deposits, and gravel pits worldwide.
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