metamorphic
Quartzite pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, brown, or light yellow due to iron oxide staining; Luster: Vitreous to dull; Structure: Granoblastic (interlocking quartz grains); Cleavage: None; SG: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, brown, or light yellow due to iron oxide staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, brown, or light yellow due to iron oxide staining; Luster: Vitreous to dull; Structure: Granoblastic (interlocking quartz grains); Cleavage: None; SG: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically in orogenic belts. This specific smooth shape results from fluvial or glaciofluvial erosion and transport.
Uses & applications
Used in construction as crushed stone for road ballast, as a refractory material in glass making, and as decorative landscaping stones.
Geological facts
Quartzite is so tough that it often survives the weathering process much longer than surrounding rocks, forming high ridges or being found as rounded pebbles in distant riverbeds.
Field identification & locations
Identify by its hardness (cannot be scratched by a steel knife) and its grainy, crystalline texture that breaks through the grains rather than around them. Found globally in riverbeds and glacial tills.
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