metamorphic
Quartzite Cobble
Quartzite (SiO2 based)
Hardness: 7 on Mohs scale; Color: Tan, orange-brown, or yellow-brown due to iron staining; Luster: Vitreous to waxy when wet; Structure: Granular, non-foliated; Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Tan, orange-brown, or yellow-brown due to iron staining
- Luster
- Vitreous to waxy when wet
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, orange-brown, or yellow-brown due to iron staining; Luster: Vitreous to waxy when wet; Structure: Granular, non-foliated; Specific Gravity: 2.6-2.7.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. This specific specimen has been rounded and smoothed by water transport in a river or glacial environment.
Uses & applications
Used as decorative garden stone, construction aggregate, and occasionally for primitive tools or flintknapping. Highly valued for durability in landscaping.
Geological facts
Quartzite is so hard that it will scratch glass and even high-quality steel. It is one of the most chemically and physically resistant rocks on Earth's surface.
Field identification & locations
Identify by its hardness (scratches glass) and its sugary, crystalline texture on a fresh break. Common in riverbeds, glacial tills, and mountainous regions worldwide.
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