metamorphic
Red Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Reddish-brown to maroon; Luster: Vitreous to dull; Crystal structure: Non-foliated, granoblastic; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Reddish-brown to maroon
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-brown to maroon; Luster: Vitreous to dull; Crystal structure: Non-foliated, granoblastic; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone. Under intense heat and pressure, the sand grains recrystallize and fuse together. The red color is typically due to trace amounts of iron oxide (hematite).
Uses & applications
Used in construction as road ballast, railway ballast, and decorative stone. Sometimes used for countertops, floor tiles, and as a raw material in the manufacture of glass and ceramics.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than along their boundaries, unlike sandstone. It is often found in the roots of mountain ranges where folding and faulting occur.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and its grainy, crystalline appearance. It is commonly found in areas of old metamorphic rock like the Appalachian Mountains or the Canadian Shield.
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