metamorphic
Quartzite Pebble (River Rock)
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Tan, brown, reddish-pink (due to iron oxides); Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, brown, reddish-pink (due to iron oxides)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, brown, reddish-pink (due to iron oxides); Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure, typically during mountain-building events. This specific specimen has been further shaped and smoothed by fluvial or glacial transport over thousands of years.
Uses & applications
Used primarily in construction as crushed stone for road beds or railroad ballast. Polished versions are used in landscaping, river rock decor, and as aquarium gravel.
Geological facts
Quartzite is one of the most durable rocks on Earth's surface. Because it is so hard and chemically stable, it often survives the erosion of surrounding softer rocks, remaining as rounded pebbles in riverbeds and on beaches.
Field identification & locations
Identify in the field by its hardness (it will easily scratch glass) and lack of visible grains compared to sandstone. Look for it in riverbeds, gravel pits, and glacial till worldwide.
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