metamorphic
Quartzite Pebble
Metamorphic Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: tan, grey, or off-white; Luster: dull to vitreous; Structure: granular/crystalline; Cleavage: none (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- tan, grey, or off-white
- Luster
- dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: tan, grey, or off-white; Luster: dull to vitreous; Structure: granular/crystalline; Cleavage: none (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during tectonic mountain-building events. These specific river-worn pebbles are often millions of years old.
Uses & applications
Used in construction as crushed stone or aggregate, as a high-silica raw material in glass making, and as decorative landscaping stones.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock layers, which is why it is frequently found as rounded pebbles in riverbeds or on beaches long after the parent rock has eroded.
Field identification & locations
Identify by its ability to easily scratch glass and its grainy, sandpaper-like surface that does not rub off. Common in glacial till, riverbeds, and ancient mountain belts. Look for a 'sugary' texture on fresh breaks.
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