metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: tan, yellow, orange due to iron staining; Luster: vitrous to dull; Crystal structure: Trigonal/Microcrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.63 - 2.65
- Hardness
- 7 (Mohs scale)
- Color
- tan, yellow, orange due to iron staining
- Luster
- vitrous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: tan, yellow, orange due to iron staining; Luster: vitrous to dull; Crystal structure: Trigonal/Microcrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.63 - 2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure reciprocal to tectonic activities cause the quartz grains to recrystallize and fuse together into a dense, hard rock.
Uses & applications
Used as crushed stone for road construction, railway ballast, and as a raw material in the glass and silicate industry. Specifically attractive specimens are used for landscaping or as decorative garden stones.
Geological facts
Quartzite is so hard that when it breaks, it breaks through the quartz grains rather than around them, unlike its parent rock sandstone. It is highly resistant to chemical weathering.
Field identification & locations
Identify by its ability to scratch glass easily and its granular, sugary texture. Look for it in mountainous regions or glacial till where it has been transported by ice. It is often found as rounded cobbles in riverbeds due to its high durability.
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