metamorphic
Quartzite
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or pinkish/tan; Luster: vitreous to grainy; Crystal Structure: Trigonal (though crystal faces are rare); Cleavage: none, usually breaks with conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or pinkish/tan
- Luster
- vitreous to grainy
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or pinkish/tan; Luster: vitreous to grainy; Crystal Structure: Trigonal (though crystal faces are rare); Cleavage: none, usually breaks with conchoidal fracture.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together, forming a dense, durable rock.
Uses & applications
Used in construction as crushed stone for roadbeds, as roofing granules, and as a decorative stone in landscaping. High-purity quartzite is used to produce glass and metallic silicon.
Geological facts
Quartzite is so hard that it will often break across the individual sand grains rather than around them. It is one of the most resistant rocks to chemical weathering.
Field identification & locations
Identify in the field by its hardness (will scratch glass) and its non-foliated, sugary or crystalline texture. It is commonly found in mountainous regions where tectonic activity has occurred.
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