metamorphic
Quartzite (Beach Pebble)
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale. Color: White to translucent grey. Luster: Vitreous to dull. Crystal structure: Hexagonal (microcrystalline). No cleavage. Specific gravity: 2.6-2.7. Very durable and resistant to weathering.
- Hardness
- 7 on Mohs scale
- Color
- White to translucent grey
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale. Color: White to translucent grey. Luster: Vitreous to dull. Crystal structure: Hexagonal (microcrystalline). No cleavage. Specific gravity: 2.6-2.7. Very durable and resistant to weathering.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, often during mountain-building events. Geological age can range from Precambrian to Cenozoic depending on regional history. The specimen shown has been naturally tumbled and polished by wave action on a beach.
Uses & applications
Used as industrial abrasive, railway ballast, construction aggregate, and in decorative landscaping. Higher purity varieties are used in glass making and electronics.
Geological facts
Quartzite is so tough that it often outlasts the mountain ranges in which it formed, frequently appearing as resistant ridges or rounded 'river rocks' and beach pebbles. It is one of the most physically durable and chemically resistant rocks found at the Earth's surface.
Field identification & locations
Identify in the field by its inability to be scratched by steel, its sugary or glassy texture, and the way it breaks through quartz grains rather than around them. Common on beaches and riverbeds globally. Collectors look for 'sea glass' like smoothness and translucency.
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