metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: white to light gray; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline); Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- white to light gray
- Luster
- vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: white to light gray; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline); Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, causing the sand grains to recrystallize and fuse together. It can be found in mountain belts and Precambrian metamorphic terrains worldwide.
Uses & applications
Used as a decorative stone in architecture, as railway ballast, as a component in glass manufacturing, and for making stone tools in prehistoric times. In modern times, it is a popular material for countertops and flooring.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the ridges and peaks of mountain ranges because it resists weathering better than the surrounding rock types. It will scratch glass easily.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and its grainy, sandpaper-like texture that unlike sandstone, breaks through the grains rather than around them. Found in abundance in regions with ancient tectonic activity.
