metamorphic
Quartzite (Beach Pebble)
Quartzite (composed primarily of SiO2)
Hardness: 7 on Mohs scale; Color: Tan to milky white with slight translucency; Luster: Vitreous to waxy; Structure: Granular/crystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan to milky white with slight translucency
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan to milky white with slight translucency; Luster: Vitreous to waxy; Structure: Granular/crystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. This specific specimen has been further shaped and rounded by water erosion in a coastal or riverine environment.
Uses & applications
Used in construction as road ballast, in the glass industry (if pure), or as architectural stone. Smooth beach pebbles are popular for landscaping, home decor, and 'rock tumbling' hobbies.
Geological facts
Quartzite is so hard that it can scratch glass and steel. It is often more durable than the parent sandstone it originated from, which is why it frequently survives as rounded pebbles on beaches long after other rocks have eroded away.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a knife) and its grainy, 'sugary' texture when viewed closely. Common in glacial till and coastal areas. Collectors look for unique translucency or interesting iron-staining colors.
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