metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 (Mohs scale); Color: Tan, beige, or light brown; Luster: Dull to vitreous; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Tan, beige, or light brown
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, beige, or light brown; Luster: Dull to vitreous; 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. High heat and pressure in regional metamorphic zones cause quartz grains to recrystallize and fuse together. These pebbles are often rounded by water action in rivers or coastal environments.
Uses & applications
Used as a major component in the glass industry, as construction aggregate, for railway ballast, and in some metallurgical processes. Polished pebbles are used in landscaping and aquariums.
Geological facts
Quartzite is so strong and resistant to weathering that it often forms the tops of ridges and mountains. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a knife) and its grainy, sugary appearance despite being a solid rock. Commonly found in riverbeds, glacial deposits, and mountain outcrops.
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