metamorphic
Quartzite Pebble
Metamorphic Quartzite
Hardness of 7 on the Mohs scale, colors ranging from tan to brown and gray, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, conchoidal fracture, specific gravity of approximately 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, colors ranging from tan to brown and gray, vitreous to greasy luster, massive crystal structure with interlocking quartz grains, conchoidal fracture, specific gravity of approximately 2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically in mountain-building or tectonic plate collision zones. Often shaped into smooth pebbles through water transport in rivers or beaches.
Uses & applications
Used in construction, railroad ballast, road aggregate, manufacturing of silica bricks, and occasionally as decorative landscaping stones or tumbling rough.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why quartz-rich sandstone units often survive as ridges or resistant pebbles long after surrounding rocks have eroded away.
Field identification & locations
Can be identified in the field by its high hardness (scratches glass easily), lack of effervescence with acid, and the sugary, interlocking crystalline texture visible on freshly broken surfaces.
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