metamorphic
Red Quartzite
Quartzite (primarily SiO2 with hematite inclusions)
Hardness: 7 on Mohs scale; Color: Reddish-brown to maroon; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular); Cleavage: None (conchoidal to irregular 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: Trigonal/Hexagonal (granular); Cleavage: None (conchoidal to irregular fracture); Specific gravity: 2.6 - 2.7
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. Under high heat and pressure, quartz grains recrystallize and fuse together. The red color is typically due to the presence of iron oxide (hematite) during formation.
Uses & applications
Used in construction as crushed stone for road beds, railway ballast, and as a decorative stone in landscaping. High-purity quartzite is used to produce silica sand for glassmaking and industrial abrasives.
Geological facts
Quartzite is so tough that it often survives intense weathering better than the surrounding rocks, frequently forming the tops of ridges and resistant hills known as 'monadnocks'.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass and steel) and its crystalline, sugary texture on fresh breaks. Common in Precambrian shield areas and folded mountain belts like the Appalachians or the Baraboo Range.
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