metamorphic
Quartzite
Quartzite (composed primarily of SiO2)
Hardness: 7 on Mohs scale; Color: white to light gray or pinkish; Luster: vitreous (glassy) to dull; Crystal structure: Trigonal (granular texture); Cleavage: none; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- white to light gray or pinkish
- Luster
- vitreous (glassy) to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: white to light gray or pinkish; Luster: vitreous (glassy) to dull; Crystal structure: Trigonal (granular texture); Cleavage: none; Specific gravity: 2.6-2.7
Formation & geological history
Quartzite forms from the metamorphism of quartz-rich sandstone. High heat and pressure cause the original quartz grains to recrystallize and fuse together into a dense, hard mass, typically in orogenic (mountain-building) belts.
Uses & applications
Used in construction for road ballast, roofing granules, and as a decorative stone in landscaping or interior design. Because of its hardness, it is also used as an abrasive.
Geological facts
Quartzite is so hard that it will scratch glass and steel. It is often distinguished from sandstone because it fractures through the quartz grains rather than around them.
Field identification & locations
Identify in the field by its extreme hardness and granular, sugary appearance. It is commonly found in mountain ranges such as the Appalachians or the Alps. For collectors, it is a great example of contact or regional metamorphism.
