metamorphic
Quartzite pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-purple to white; Luster: Vitreous to dull; Crystal structure: Non-foliated, interlocking quartz grains; Cleavage: None; Specific gravity: 2.6-2.65.
- Hardness
- 7 on Mohs scale
- Color
- Grayish-purple to white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-purple to white; Luster: Vitreous to dull; Crystal structure: Non-foliated, interlocking quartz grains; Cleavage: None; Specific gravity: 2.6-2.65.
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, typically during tectonic plate collisions and mountain-building events. This specimen has been rounded into a pebble by water erosion.
Uses & applications
Commonly used as construction aggregate, railway ballast, and decorative stone in landscaping. High-purity quartzite is used to produce glass and industrial silica.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock in weathering processes, resulting in the rounded pebbles often found in riverbeds and on beaches. It is much harder than the sandstone it originates from.
Field identification & locations
Identify in the field by its hardness (will scratch glass easily) and its sugary, granular texture. Unlike marble, it will not fizz with acid. Common in ancient mountain belts and river deposits.
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