metamorphic
Quartzite Cobble
Quartzite (composed primarily of SiO2)
Hardness: 7 on Mohs scale. Color: greyish-brown with white quartz veining. Luster: dull to vitreous. Crystal structure: Granoblastic. Cleavage: None. Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- greyish-brown with white quartz veining
- Luster
- dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale. Color: greyish-brown with white quartz veining. Luster: dull to vitreous. Crystal structure: Granoblastic. Cleavage: None. Specific gravity: 2.6-2.7.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. This specimen shows significant rounding and smoothing due to fluvial (river) or glacial transport processes.
Uses & applications
Commonly used as crushed stone in construction, road ballast, and as decorative landscaping stones or garden features.
Geological facts
Quartzite is so tough that it can withstand millions of years of weathering; it often forms the resistant caps of mountains or ridges. The white lines visible are secondary quartz veins that filled fractures in the rock.
Field identification & locations
Identify by its extreme hardness (will scratch glass easily) and its sugary, granular texture. Look for it in riverbeds, glacial tills, and mountainous regions where ancient sedimentary basins were uplifted.
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