metamorphic
Quartzite Pebble (River Rock)
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Off-white to light tan; Luster: Dull/granular when dry, vitreous when wet; Crystal structure: Non-foliated/Granoblastic; Specific gravity: approx 2.65.
- Hardness
- 7 on Mohs scale
- Color
- Off-white to light tan
- Luster
- Dull/granular when dry, vitreous when wet
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Physical properties
Hardness: 7 on Mohs scale; Color: Off-white to light tan; Luster: Dull/granular when dry, vitreous when wet; Crystal structure: Non-foliated/Granoblastic; Specific gravity: approx 2.65.
Formation & geological history
Formed from the regional metamorphism of quartz-rich sandstone. High heat and pressure fused quartz grains into a solid mass. This specific specimen has been smoothed and rounded by river or coastal hydraulic action over many years.
Uses & applications
Used in landscaping, architectural facing, decorative garden features, and sometimes as a crushed aggregate for road construction.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the crests of ridges and peaks in mountain ranges. It is harder than a steel knife and will easily scratch glass.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a knife) and sugary/granular texture. It lacks the reaction to acid seen in marble. Common in glaciated regions and riverbeds.
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