metamorphic
Quartzite pebble
Metamorphic rock (mainly SiO2)
Hardness: 7 (Mohs scale); Color: Brownish-yellow, tan, or grey; Luster: Vitreous to dull; Crystal structure: Non-foliated/Granoblastic; Cleavage: None; Specific Gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Brownish-yellow, tan, or grey
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Brownish-yellow, tan, or grey; Luster: Vitreous to dull; Crystal structure: Non-foliated/Granoblastic; Cleavage: None; Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. This specific specimen is a water-worn river or beach pebble.
Uses & applications
Used as a decorative garden stone, in construction aggregate, as a durable building material, and occasionally for lapidary tumbling.
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 after millions of years of erosion.
Field identification & locations
Identify by its extreme hardness (it will scratch glass) and lack of distinct graininess compared to sandstone. It is found globally in mountainous and coastal regions.
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