metamorphic
Grey Quartzite Pebble
Quartzite (primarily SiO2 - Silicon Dioxide)
Hardness: 7 on Mohs scale; Color: light grey with darker internal banding; Luster: vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture); Specific gravity: approx 2.65.
- Hardness
- 7 on Mohs scale
- Color
- light grey with darker internal banding
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: light grey with darker internal banding; Luster: vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture); Specific gravity: approx 2.65.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. This specimen has been significantly water-worn into a smooth pebble shape through fluvial or coastal erosion. Geological age can range from Precambrian to Mesozoic depending on source region.
Uses & applications
Quartzite is used heavily in the construction industry as crushed stone for road ballast, floor tiles, and countertop surfaces. Rounded pebbles are popular for landscaping and decorative accents.
Geological facts
Quartzite is much harder and more resistant to weathering than its parent rock, sandstone. Because of its hardness, it remains in the environment long after other rocks have eroded away, which is why smooth quartzite pebbles are common on shorelines.
Field identification & locations
Identify in the field by checking for its ability to scratch glass and its granular, sugary texture on freshly broken surfaces. It will not react with acid, distinguishing it from limestone or marble. It is a very common find in river beds and on beaches globally.
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