metamorphic
Quartzite
Quartzite (Primary mineral: SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan (like the specimen shown); Luster: vitreous to dull; Crystal structure: granular/clastic; Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or tan (like the specimen shown)
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or tan (like the specimen shown); Luster: vitreous to dull; Crystal structure: granular/clastic; Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed from the regional or contact metamorphism of quartz sandstone. Under intense heat and pressure, the individual quartz grains recrystallize and fuse together into a dense, interlocking mosaic of crystals.
Uses & applications
Used widely in construction as crushed stone for road gravel and rail ballast, as dimension stone for wall coverings and flooring, and occasionally in jewelry as a substitute for more expensive white gemstones.
Geological facts
Quartzite is so tough that it often survives erosion better than any other rock type, forming the caps of many mountain ranges. It is chemically stable and resistant to weathering.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass and steel) and its granular appearance that looks somewhat like sugar crystals fused together. It is very common in metamorphic belts and can be found globally.
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