metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: light grey to beige, Luster: dull to vitreous when polished, Crystal structure: trigonal (microcrystalline), Cleavage: none, Specific gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: light grey to beige, Luster: dull to vitreous when polished, Crystal structure: trigonal (microcrystalline), Cleavage: none, Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure. This specific specimen is a river-worn or beach pebble, shaped by water erosion.
Uses & applications
Used primarily as decorative gravel, in landscaping, as a construction aggregate, and occasionally in glassmaking if pure. Smooth pebbles are also used in massage therapy and crafts.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the caps of mountains and ridges. Because it consists of interlocked quartz grains, it is much tougher than the sandstone it originated from.
Field identification & locations
Can be identified by its extreme hardness (will scratch steel) and sugary, granular texture hidden beneath the smooth surface. Common in riverbeds, glacial deposits, and beaches globally.
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