metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Pinkish-orange (due to iron oxide inclusions); Luster: Vitreous to dull; Crystal structure: Hexagonal/Trigonal (individual grains); Cleavage: None (conchoidal fracture); SG: 2.6 - 2.65
- Hardness
- 7 on Mohs scale
- Color
- Pinkish-orange (due to iron oxide inclusions)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Pinkish-orange (due to iron oxide inclusions); Luster: Vitreous to dull; Crystal structure: Hexagonal/Trigonal (individual grains); Cleavage: None (conchoidal fracture); SG: 2.6 - 2.65
Formation & geological history
Formed through the regional metamorphism of quartz sandstone. Intense heat and pressure cause the sand grains to recrystallize and fuse together, forming an interlocking mosaic of quartz crystals. Most often found in mountain belts and Precambrian shields.
Uses & applications
Used in various construction applications including road ballast, railway tracks, and decorative building stone. It is also used as a source of silica in glass manufacturing and as an abrasive in industrial processes.
Geological facts
Quartzite is so tough that it often survives erosion better than other rocks, forming prominent ridges or mountain peaks. Unlike sandstone, when quartzite is broken, it fractures through the individual sand grains rather than around them.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and granular, sugary appearance on fresh surfaces. Often found in proximity to other metamorphic rocks like schist or gneiss. Look for a dense, non-foliated texture.
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