metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Tan, white, and yellowish-brown with iron staining; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65
- Hardness
- 7 on Mohs scale
- Color
- Tan, white, and yellowish-brown with iron staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, white, and yellowish-brown with iron staining; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under high heat and pressure, causing recrystallization. This specimen shows significant rounding and smoothing from fluvial (river) or glacial transport over thousands of years.
Uses & applications
Used as aggregate in construction, road ballast, and decorative landscaping. High-purity quartzite is used to produce silica sand for glassmaking and silicon for electronics.
Geological facts
Quartzite is so durable that it often remains as 'river cobbles' long after the surrounding softer rocks have eroded away. It is harder than steel and will easily scratch glass or a knife blade.
Field identification & locations
Identify in the field by its hardness (it cannot be scratched by a steel nail) and its granular, sugary texture when broken. Commonly found in riverbeds, glacial tills, and decorative gravel pits across North America and Europe.
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