metamorphic
Quartzite Pebble
Quartzite (principally SiO2)
Hardness: 7 Mohs scale; Color: Sandy yellow to tan; Luster: Dull to vitreous; Crystal structure: Trigonal (granular); Cleavage: None; Specific gravity: 2.6-2.7.
- Hardness
- 7 Mohs scale
- Color
- Sandy yellow to tan
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 Mohs scale; Color: Sandy yellow to tan; Luster: Dull to vitreous; Crystal structure: Trigonal (granular); Cleavage: None; Specific gravity: 2.6-2.7.
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 of quartz crystals.
Uses & applications
Used as decorative gravel, in landscaping, as a construction aggregate, and occasionally in the manufacture of glass or ceramics due to high silica content.
Geological facts
Quartzite is so tough that it often survives the weathering process that breaks down surrounding rocks, which is why it is frequently found as rounded river pebbles or coastal cobbles.
Field identification & locations
Identify in the field by its extreme hardness (it will scratch glass) and its sugary, granular appearance on fresh surfaces. Often found in riverbeds, glacial deposits, and mountain ranges.
