metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: White, gray, or tan with potential mineral staining; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal microcrystalline; Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- White, gray, or tan with potential mineral staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: White, gray, or tan with potential mineral staining; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal microcrystalline; Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone subjected to high heat and pressure, causing the original quartz grains to recrystallize into an interlocking mosaic. This specific specimen reflects secondary mechanical weathering (rounding) in a high-energy aquatic environment such as a river or coastal beach.
Uses & applications
Used in construction as crushed stone or ballast, in high-end architecture as decorative stone, and as a source of silica in glassmaking and metallurgy. Smooth pebbles like this are popular for landscaping, terrariums, and craft projects.
Geological facts
Quartzite is so durable that it often remains as ridges or outcrops long after surrounding softer rocks like limestone or shale have eroded away. Rounded pebbles like this are often referred to as 'river rocks' and can survive thousands of miles of transport.
Field identification & locations
Identify by its hardness (it will scratch glass and steel) and lack of reaction to acid. Commonly found in glaciofluvial deposits, riverbeds, and beaches across North America and Europe. For collectors, look for high-purity white or translucent specimens.
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