metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 (Mohs), Color: white to light gray, Luster: vitreous to waxy, Crystal structure: Trigonal (microcrystalline), Cleavage: None/Conchoidal fracture, Specific gravity: 2.63-2.65
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Physical properties
Hardness: 7 (Mohs), Color: white to light gray, Luster: vitreous to waxy, Crystal structure: Trigonal (microcrystalline), Cleavage: None/Conchoidal fracture, Specific gravity: 2.63-2.65
Formation & geological history
Formed when quartz-rich sandstone is subjected to heat, pressure, and chemical activity of metamorphism, causing the sand grains to recrystallize into an interlocking mosaic. Found in orogenic belts and riverbeds.
Uses & applications
Used as a decorative stone, in construction as aggregate or road ballast, and as a source for silica in glassmaking. Polished pebbles are used in landscaping and aquariums.
Geological facts
Quartzite is so tough that it often breaks through the quartz grains rather than around them. It is one of the most chemically and physically resistant rocks on the Earth's surface.
Field identification & locations
Identify by its hardness (it will scratch glass) and its sugary, granular texture that looks like sandpaper but is smooth to the touch. Commonly found in river beds and decorative garden mulches.
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