metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: Cream, white, or light gray with brown inclusions; Luster: Vitreous to waxy after polishing; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None/Conchoidal fracture; Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Cream, white, or light gray with brown inclusions
- Luster
- Vitreous to waxy after polishing
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Physical properties
Hardness: 7 on Mohs scale; Color: Cream, white, or light gray with brown inclusions; Luster: Vitreous to waxy after polishing; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None/Conchoidal fracture; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically in convergent plate boundaries. This specific specimen has been rounded and smoothed by water erosion in a river or beach environment.
Uses & applications
Used in landscaping, as tumbling media for hobbyists, and in construction as crushed stone or decorative aggregate. High-purity quartzite is used in glass making.
Geological facts
Quartzite is so hard that it will scratch glass and even high-quality steel. It is more resistant to weathering than the sandstone it originated from, often forming the caps of ridges and mountains.
Field identification & locations
Identify in the field by its extreme hardness and the way it breaks through quartz grains rather than around them (unlike sandstone). Commonly found in glaciated areas or riverbeds draining mountainous regions.
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