metamorphic
Quartzite Pebble
Metamorphic Quartzite
Hardness of 7 on the Mohs scale, grayish-purple color, vitreous to greasy luster, non-foliated massive crystal structure, conchoidal fracture, specific gravity around 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, grayish-purple color, vitreous to greasy luster, non-foliated massive crystal structure, conchoidal fracture, specific gravity around 2.65.
Formation & geological history
Formed from quartz-rich sandstone or chert that has been subjected to intense heat and pressure, typically during regional or contact metamorphism over millions of years.
Uses & applications
Used in construction, as aggregate, for railway ballast, in the manufacture of silica brick, and sometimes tumbled or polished for decorative stones and jewelry.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why quartz-rich rocks often survive long journeys in rivers and oceans to become smooth pebbles.
Field identification & locations
Can be identified in the field by its hardness (scratches glass easily), lack of fizz with acid, and the fused quartz grains visible on fresh breaks. Found worldwide in ancient orogenic belts.
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