metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or reddish-brown due to iron impurities; Luster: vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: none; Specific gravity: approx 2.65.
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or reddish-brown due to iron impurities; Luster: vitreous to dull; Crystal structure: Trigonal (granular texture); Cleavage: none; Specific gravity: approx 2.65.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. Under high heat and pressure, the individual quartz grains recrystallize and fuse into a dense, interlocking mosaic. Most common in Precambrian and Paleozoic rock formations.
Uses & applications
Used as crushed stone in construction and road building, as a component in glass manufacturing, for refractory bricks in furnaces, and as decorative stone for countertops and walls.
Geological facts
Quartzite is so tough that it often breaks through the quartz grains rather than along the boundaries between them. It is highly resistant to chemical weathering and creates prominent ridges in many mountain ranges.
Field identification & locations
Identify in the field by its hardness (scratches glass/steel) and grainy 'sugary' texture. Unlike marble, it will not fizz with acid. Common in the Appalachian Mountains, Lake Superior region, and Brazil.
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