metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, beige, or pale orange-red from iron oxides; Luster: Vitreous to dull; Crystal structure: Non-foliated, interlocking quartz grains; Cleavage: None (conchoidal fracture); Specific gravity: 2.6 to 2.7.
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, or pale orange-red from iron oxides
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, beige, or pale orange-red from iron oxides; Luster: Vitreous to dull; Crystal structure: Non-foliated, interlocking quartz grains; Cleavage: None (conchoidal fracture); Specific gravity: 2.6 to 2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together into a dense, hard rock. Found in mountain ranges and metamorphic belts worldwide.
Uses & applications
Used primarily as crushed stone for road construction, railway ballast, and as a decorative stone in landscaping. Its extreme hardness and resistance to chemical weathering make it a durable building material.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks; when broken, it fractures through the sand grains rather than around them, distinguishing it from sandstone. Many prehistoric tools were crafted from quartzite when flint was unavailable.
Field identification & locations
Identify by its ability to scratch glass easily and its lack of visible pores. It common in riverbeds and glacial deposits. Collectors value pieces with unique colors or surface textures created by natural erosion.
