metamorphic
Quartzite Cobble
Meta-quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: White to light tan with iron staining; Luster: Vitreous to dull; Crystal structure: Non-foliated granoblastic; Cleavage: None/Conchoidal fracture; Specific gravity: 2.63 - 2.65
- Hardness
- 7 (Mohs scale)
- Color
- White to light tan with iron staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: White to light tan with iron staining; Luster: Vitreous to dull; Crystal structure: Non-foliated granoblastic; Cleavage: None/Conchoidal fracture; Specific gravity: 2.63 - 2.65
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 in construction as road ballast, railway beds, and decorative landscaping. High-purity quartzite is used to produce glass and silicon metal.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in a landscape, leading to the formation of ridges and hills. It is harder than steel and will scratch a glass plate easily.
Field identification & locations
Identify in the field by its sugary texture on fresh surfaces and its inability to be scratched by a steel knife. Common in ancient riverbeds and mountainous metamorphic belts.
