metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: White to light grey with tan/rust staining; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- White to light grey with tan/rust staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: White to light grey with tan/rust staining; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed from the recrystallization of quartz-rich sandstone through intense heat and pressure associated with tectonic compression. This specific specimen has been rounded into a pebble by fluvial (river) or glacial transport over thousands of years.
Uses & applications
Used primarily in construction as crushed stone for road gravel or railway ballast. High-purity quartzite is used to produce ferrosilicon and silicon metal. It is also used as decorative landscaping stone.
Geological facts
Quartzite is so touch that it will easily scratch glass and stainless steel. It is more resistant to weathering than most other rocks, which is why it often survives as rounded pebbles in riverbeds and on beaches long after softer rocks have eroded.
Field identification & locations
Identify in the field by its extreme hardness (shards can scratch glass) and its sugary, granular texture. It is commonly found in ancient mountain belts and river basins globally. For a collector, it represents a classic example of metamorphic transformation.
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