metamorphic
Quartzite
Quartzite (SiO2)
Hardness 7 on Mohs scale; light gray, tan, to yellowish-brown weathered surface; dull to vitreous luster; granular, sugary texture; tough and resistant to weathering; no distinct cleavage.
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Physical properties
Hardness 7 on Mohs scale; light gray, tan, to yellowish-brown weathered surface; dull to vitreous luster; granular, sugary texture; tough and resistant to weathering; no distinct cleavage.
Formation & geological history
Formed through the regional metamorphic alteration of quartz sandstone under high heat and pressure, causing quartz grains to recrystallize and fuse together solidly.
Uses & applications
Used in construction as crushed stone for road base, railway ballast, building stone, decorative landscaping stone, and as a source of silica in glass and industrial applications.
Geological facts
Quartzite is so hard that when struck with a hammer, it breaks through the quartz grains rather than along the boundaries between them, unlike sandstone.
Field identification & locations
Identify in the field by its sugary recrystallized appearance and extreme hardness (scratches glass easily and cannot be scratched by a steel blade). Commonly found in mountainous metamorphic terrains globally.
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