metamorphic
Quartzite Pebble
Metamorphic Quartzite (SiO2)
Hardness: 7 on the Mohs scale. Color: Pale tan, cream, grayish-yellow. Luster: Dull to earthy when raw, vitreous to waxy on smooth worn surfaces. Structure: Granoblastic texture, non-foliated. Cleavage: None (conchoidal to irregular fracture).
- Hardness
- 7 on the Mohs scale
- Color
- Pale tan, cream, grayish-yellow
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Physical properties
Hardness: 7 on the Mohs scale. Color: Pale tan, cream, grayish-yellow. Luster: Dull to earthy when raw, vitreous to waxy on smooth worn surfaces. Structure: Granoblastic texture, non-foliated. Cleavage: None (conchoidal to irregular fracture).
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone under intense heat and pressure, recrystallizing quartz grains into a dense, interlocking matrix. Frequently rounded into smooth pebbles by water erosion in rivers or coastal environments.
Uses & applications
Used in aggregate construction, landscaping, stone carving, and ballast. High-purity quartzite is also used to produce silicon metal and glass.
Geological facts
Because quartzite consists almost entirely of tightly interlocking quartz grains, it is extremely tough and highly resistant to chemical and physical weathering, allowing pebbles like this to survive long transport down riverbeds.
Field identification & locations
Identified in the field by its hardness (scratches glass easily), sugary micro-crystalline appearance, and smooth, water-worn beach or river cobble form. Common worldwide in fluvial and glacial deposits.
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