metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Tan, grey, or white; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, grey, or white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, grey, or white; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz sandstone under intense heat and pressure, typically in orogenic belts (mountain building locations). This specific specimen has been rounded by fluvial or coastal erosion.
Uses & applications
Used in construction as road ballast, in glass manufacturing if high purity, as an abrasive, and frequently used in landscaping.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, often forming the caps of ridges and mountains. It is harder than a steel knife and will easily scratch glass.
Field identification & locations
Identify in the field by its extreme hardness and grainy, sugary texture that resembles sandstone but does not break around the grains. Common in riverbeds and beaches globally.
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