metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale. Color: White to light gray. Luster: Vitreous to dull. Crystal structure: Trigonal (microcrystalline/interlocking). Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- White to light gray
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale. Color: White to light gray. Luster: Vitreous to dull. Crystal structure: Trigonal (microcrystalline/interlocking). Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together. These pebbles are typically smoothed by water erosion in riverbeds or coastal environments.
Uses & applications
Used in construction as a decorative stone, aggregate for roads, and railroad ballast. Highly durable, it is also used for tool-making historically and as a landscaping material today.
Geological facts
Quartzite is so hard that it can scratch steel and glass easily. Unlike sandstone, when quartzite breaks, it fractures through the quartz grains rather than around them due to the intense fusion of the silica.
Field identification & locations
Identify in the field by its extreme hardness and sugary, crystalline texture under a hand lens. It will not bubble with acid (unlike marble or limestone) and is often found as smooth, rounded white pebbles in beach or stream deposits.
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