metamorphic
Quartzite Pebble
Quartzite (mostly SiO2)
Hardness: 7 on Mohs scale; Color: Tan to yellowish-brown; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Tan to yellowish-brown
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan to yellowish-brown; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure, causing recrystallization of quartz grains. The smooth shape indicates water-worn erosion in a river or coastal environment.
Uses & applications
Industrial use as a source of silica, railway ballast, and decorative landscaping stones. Tumbled pebbles like this are used in home decor and pebble mulch.
Geological facts
Quartzite is so durable that it often survives intense weathering better than the surrounding rocks, leading to its accumulation in riverbeds and beaches. It is harder than steel and will scratch glass easily.
Field identification & locations
Identify in the field by its hardness (will not be scratched by a knife) and its grainy but fused appearance. Found globally in areas of ancient mountain building and alluvial deposits.
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