metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale), Color: tan, grey, or white; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline quartz grains); Cleavage: none; Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale), Color: tan, grey, or white
- Color
- tan, grey, or white
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale), Color: tan, grey, or white; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline quartz grains); Cleavage: none; Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically in orogenic belts. This specific specimen has been further shaped by fluvial or coastal transport, resulting in its smooth, rounded 'pebble' form.
Uses & applications
Used as aggregate in construction, railway ballast, and sometimes as a decorative stone in landscaping. High-purity quartzite is used to produce ferrosilicon and silica sand for glassmaking.
Geological facts
Quartzite is so tough that it often outlasts other rock types during weathering, frequently standing out as ridges or hills. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a knife) and its grainy, sandpaper-like texture despite being smooth. Found globally in riverbeds, beaches, and ancient glacial deposits.
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