metamorphic
Quartzite
Quartzite (consisting primarily of SiO2)
Hardness: 7 on Mohs scale; Color: Pink, reddish-brown, tan; 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
- Pink, reddish-brown, tan
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Pink, reddish-brown, tan; Luster: Vitreous to dull; Crystal structure: Non-foliated granoblastic; 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, the sand grains recrystallize and fuse together, losing original sedimentary textures. Frequently associated with Precambrian and Paleozoic orogenies.
Uses & applications
Used as a decorative stone in landscaping, crushed stone for road construction, railway ballast, and occasionally for high-end countertops or tiles due to its extreme durability and hardness.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than around them, unlike its parent rock sandstone. It is highly resistant to chemical weathering and often forms prominent ridges or mountain peaks.
Field identification & locations
Identify in the field by its hardness (it should easily scratch glass) and its sugary texture. It is commonly found in mountain ranges such as the Appalachians or the Rockies. This specimen shows iron oxide staining giving it its pinkish-red hue.
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