metamorphic
Quartzite (Meta-sedimentary)
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: white to light gray (pinkish due to iron impurities); Luster: Vitreous to dull/sugary; Crystal structure: Trigonal/Hexagonal crystals within a fused granular structure; Specific gravity: approx. 2.65
- Hardness
- 7 on Mohs scale
- Color
- white to light gray (pinkish due to iron impurities)
- Luster
- Vitreous to dull/sugary
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Physical properties
Hardness: 7 on Mohs scale; Color: white to light gray (pinkish due to iron impurities); Luster: Vitreous to dull/sugary; Crystal structure: Trigonal/Hexagonal crystals within a fused granular structure; Specific gravity: approx. 2.65
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together into a dense, hard rock.
Uses & applications
Used extensively in construction as crushed stone, road ballast, and decorative stone. High-purity quartzite is used to produce glass, ferrosilicon, and silicon metal.
Geological facts
Quartzite is so hard that it will break through the quartz grains rather than along the boundaries between them, unlike sandstone. It is highly resistant to chemical weathering and often forms the peaks of mountain ranges.
Field identification & locations
Identify in the field by its extreme hardness (scratches glass) and sugary, crystalline texture. It is commonly found in ancient fold mountain belts like the Appalachians or the Scottish Highlands.
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