metamorphic
Quartzite Pebble
Metamorphic Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Brownish-red to tan; Luster: Dull/waxy (unpolished) to vitreous; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Brownish-red to tan
- Luster
- Dull/waxy (unpolished) to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Brownish-red to tan; Luster: Dull/waxy (unpolished) to vitreous; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz sandstone under heat and pressure, typically in orogenic belts. This specific specimen has been further shaped into a water-worn pebble through fluvial or glacial transport during the Quaternary period.
Uses & applications
Used as decorative landscaping stone, in construction aggregates, and occasionally as a source of silica for industrial glass making. Rounded pebbles are popular in decorative pebble mosaics.
Geological facts
Quartzite is so hard that it will scratch glass and steel. It is more resistant to weathering than the original sandstone it formed from, which is why quartzite pebbles often persist long after other materials have eroded.
Field identification & locations
Identified in the field by its extreme hardness, lack of fizzing with acid (unlike limestone), and grainy texture beneath a smooth surface. Found globally in riverbeds, beaches, and glacial deposits.
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