metamorphic
Quartzite (Yellow/Tan)
Metamorphic Rock composed of Quartz (SiO₂)
Hardness: 7 on Mohs scale; Color: yellowish-tan with possible iron staining; 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
- yellowish-tan with possible iron staining
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: yellowish-tan with possible iron staining; 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 sandstone. Subjected to high heat and pressure, causing original quartz sand grains to recrystallize and fuse into a dense, interlocking network of crystals.
Uses & applications
Used primarily as crushed stone for road construction and railway ballast. Due to its hardness and resistance to weathering, it is also used for decorative landscaping, floor tiles, and as a refractory material in glass and metal production.
Geological facts
Quartzite is so hard that if you hit it with a hammer, it will typically break through the original sand grains rather than around them, unlike its parent stone, sandstone. It is often found as a 'residual' rock because it is more resistant to erosion than the stones surrounding it.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel pocket knife) and its grainy, crystalline texture that lacks the layers seen in slate or gneiss. Common in mountain ranges and glacial deposits across North America and Europe.
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