metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color:Tan, brownish, or gray with iron staining; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.63 - 2.65.
- Hardness
- 7 on Mohs scale
- Color
- Tan, brownish, or gray with iron staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color:Tan, brownish, or gray with iron staining; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.63 - 2.65.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, recrystallizing the sand grains into a dense rock. Often found as rounded river or beach stones after millions of years of erosion.
Uses & applications
Used in construction as road ballast, gravel, and in the production of glass and silicon. Polished pebbles are often used in landscaping or as decorative stones.
Geological facts
Quartzite is so hard that it will scratch glass and steel. Unlike sandstone, quartzite breaks through the quartz grains rather than around them due to its dense, interlocking structure.
Field identification & locations
Identify in the field by its hardness and lack of reaction to acid. It often has a slightly sugary or grainy appearance on fresh breaks but feels very smooth in pebble form. Commonly found in riverbeds and glacial deposits.
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