metamorphic
Quartzite
Metamorphic Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: tan, pinkish, or gray; Luster: vitreous to dull; Crystal structure: hexagonal/trigonal (as microcrystalline quartz); Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- tan, pinkish, or gray
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: tan, pinkish, or gray; Luster: vitreous to dull; Crystal structure: hexagonal/trigonal (as microcrystalline quartz); Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz sandstone. Intense heat and pressure cause the original quartz grains to recrystallize and fuse together, often in tectonic mountain-building zones.
Uses & applications
Used as a decorative stone in landscaping, construction aggregate, crushed stone for road beds, and occasionally carved into ornaments or used for high-silica industrial manufacturing.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock in weathering processes, frequently forming the tops of ridges and hills. It is often confused with marble but can be distinguished by its superior hardness.
Field identification & locations
Identify in the field by its hardness (it will scratch glass and steel) and its granular, sugary appearance on fresh surfaces. It is found globally in ancient mountain ranges and riverbeds as rounded cobbles.
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