metamorphic
Yellow Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Yellowish-tan to light brown; Luster: Dull to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.63-2.65
- Hardness
- 7 on Mohs scale
- Color
- Yellowish-tan to light brown
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Yellowish-tan to light brown; Luster: Dull to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.63-2.65
Formation & geological history
Formed from the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together, often during mountain-building events.
Uses & applications
Used in construction as crushed stone or road ballast, as dimension stone for architectural cladding and flooring, and occasionally in glassmaking if pure. Yellow varieties are sometimes used in landscaping.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock, forming prominent ridges or mountain peaks. It will break across the original sand grains rather than around them, unlike sandstone.
Field identification & locations
Identify by its extreme hardness (scratches glass), grainy texture that doesn't rub off, and its resistance to chemical weathering. Commonly found in old mountain belts and river beds as rounded cobbles.
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