metamorphic
Quartzite (Tumbled)
Recrystallized Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Creamy white to pale yellow; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal (granular texture); Cleavage: None; Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Creamy white to pale yellow
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Creamy white to pale yellow; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal (granular texture); Cleavage: None; Specific gravity: 2.65
Formation & geological history
Formed via the metamorphism of quartz-rich sandstone. Under intense heat and pressure, the sand grains recrystallize and fuse together into a dense, hard rock.
Uses & applications
Used in construction for road ballast and flooring, as a source for silica in glass manufacturing, and as decorative gravel or tumbled stones for collecting.
Geological facts
Quartzite is so strong that when it breaks, it fractures through the quartz grains themselves rather than around them, which is how it is distinguished from sandstone.
Field identification & locations
Identify by its high hardness (it cannot be scratched by a steel blade) and granular, crystalline texture. Commonly found in mountain ranges or as water-worn pebbles in rivers.
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