metamorphic
Quartzite Cobble
Metamorphic Rock (SiO2 dominated)
Hardness: 7 on Mohs scale; Color: Tan, brown, and light pink; Luster: Vitreous to dull; Structure: Granoblastic (sugary texture); Cleavage: None (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- Tan, brown, and light pink
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, brown, and light pink; Luster: Vitreous to dull; Structure: Granoblastic (sugary texture); Cleavage: None (conchoidal fracture).
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. This specimen shows significant rounding from water transport in a river or glacial environment.
Uses & applications
Used primarily as decorative landscaping stone, crushed stone for road construction, and ballast. High-purity quartzite is also a source of silica for glassmaking.
Geological facts
Quartzite is so durable that it often survives multiple cycles of erosion, outlasting the softer rocks that surround it. The color variation is due to trace amounts of iron oxides.
Field identification & locations
Identify by its ability to scratch glass and its granular, sand-like texture that does not rub off. Found globally in riverbeds, glacial tills, and mountainous regions.
