metamorphic
Quartzite Cobble
Meta-quartzite
Hardness: 7 on Mohs scale; Color: typically white, grey, or tan with reddish staining from iron oxide; Luster: dull to vitreous; Structure: granular, non-foliated; Cleavage: none, breaks through sand grains.
- Hardness
- 7 on Mohs scale
- Luster
- dull to vitreous
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, grey, or tan with reddish staining from iron oxide; Luster: dull to vitreous; Structure: granular, non-foliated; Cleavage: none, breaks through sand grains.
Formation & geological history
Formed from the metamorphism of quartz sandstone under intense heat and pressure associated with tectonic compression. This specific rounded shape indicates transport by water or glacial action.
Uses & applications
Used as aggregate in construction, railway ballast, and occasionally as decorative landscaping stones or garden features.
Geological facts
Quartzite is so durable that it can withstand millions of years of chemical weathering and mechanical erosion, often being the last rock type to disappear from a landscape.
Field identification & locations
Identified in the field by its extreme hardness (cannot be scratched by steel) and lack of reactivity to acid. It is commonly found in riverbeds, glacial tills, and mountain ranges.
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