metamorphic
Red Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Reddish-pink to light brown; Luster: Vitreous to dull; Crystal structure: Granoblastic (interlocking quartz grains); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Reddish-pink to light brown
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-pink to light brown; Luster: Vitreous to dull; Crystal structure: Granoblastic (interlocking quartz grains); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. Under high heat and pressure, quartz grains recrystallize and fuse together. The reddish color is typically due to trace amounts of iron oxide (hematite).
Uses & applications
Used as railway ballast, crushed stone for road construction, architectural stone for flooring and walls, and occasionally in jewelry as a durable decorative stone.
Geological facts
Quartzite is so tough that it often survives intense weathering that wears away surrounding softer rocks. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify in the field by its extreme hardness and sugary, crystalline texture that does not rub off like sand. Found in metamorphic belts worldwide, often in mountainous regions or as river-worn cobbles.
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