metamorphic
Quartzite pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale. Color: Tan, beige, or off-white. Luster: Vitreous to waxy when water-worn. Crystal structure: Hexagonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, or off-white
- Luster
- Vitreous to waxy when water-worn
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Physical properties
Hardness: 7 on Mohs scale. Color: Tan, beige, or off-white. Luster: Vitreous to waxy when water-worn. Crystal structure: Hexagonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. This specific rounded shape indicates transport in a high-energy water environment like a river or beach, where it underwent mechanical weathering over thousands of years.
Uses & applications
Primarily used as a construction aggregate, for railroad ballast, or as decorative landscaping stones. Smooth pebbles are often used in home decor and zen gardens.
Geological facts
Quartzite is so tough that it often outlasts the mountain ranges it was formed in, becoming resistant river gravel. It will scratch glass easily, unlike similar-looking calcite or limestone.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a steel blade) and its granular, sugary texture under a hand lens. It is ubiquitous in riverbeds and glacial deposits worldwide.
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