metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale. Color: Tan, yellowish-brown, or beige. Luster: Dull/waxy due to weathering, but vitreous when freshly broken. Crystal structure: Granoblastic (hexagonal system at mineral level). Specific gravity: 2.6 - 2.8.
- Hardness
- 7 on Mohs scale
- Color
- Tan, yellowish-brown, or beige
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Physical properties
Hardness: 7 on Mohs scale. Color: Tan, yellowish-brown, or beige. Luster: Dull/waxy due to weathering, but vitreous when freshly broken. Crystal structure: Granoblastic (hexagonal system at mineral level). Specific gravity: 2.6 - 2.8.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically in orogenic (mountain building) belts. This specific specimen has been further shaped by fluvial or alluvial erosion (water transport), rounding its edges over thousands of years.
Uses & applications
Used in construction as crushed stone or railway ballast. Its high silica content makes it valuable for manufacturing glass and silicon. Polished pebbles are used in landscaping and aquariums.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the caps of ridges and mountains because it resists weathering better than surrounding rocks. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify in the field by its hardness (it cannot be scratched by a knife) and its grainy, sugary texture on fresh surfaces. Often found in riverbeds, glacial deposits, and mountain outcrops. Look for it along coastlines or stream beds.
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