metamorphic
Quartzite River Rock
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan with green mineral inclusions; Luster: dull to vitreous; Crystal structure: granular, non-foliated; Cleavage: none; Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or tan with green mineral inclusions
- Luster
- dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan with green mineral inclusions; Luster: dull to vitreous; Crystal structure: granular, non-foliated; Cleavage: none; Specific gravity: 2.6-2.7.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. The rounded shape indicates secondary weathering as a river cobble over thousands of years.
Uses & applications
Used in construction as crushed stone or road ballast, in glass manufacturing if pure, and frequently as decorative landscaping stones.
Geological facts
Quartzite is so hard it will scratch glass and even steel. It is one of the most durable rocks on Earth's surface, often outlasting the mountains it formed within.
Field identification & locations
Identify in the field by its sugary, granular texture and extreme hardness. Common in mountainous regions or ancient riverbeds. To collect, look for smooth, water-worn shapes in gravel pits or creek banks.
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