metamorphic
Quartzite
Quartzite (composed primarily of SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: typically white to gray, yellowish, or reddish; Luster: vitreous to pearly; Crystal structure: hexagonal (polycrystalline); Cleavage: none (conchoidal fracture). It has a distinct sparkly or sugary appearance due to the recrystallized quartz grains.
- Hardness
- 7 on Mohs scale
- Color
- typically white to gray, yellowish, or reddish
- Luster
- vitreous to pearly
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, yellowish, or reddish; Luster: vitreous to pearly; Crystal structure: hexagonal (polycrystalline); Cleavage: none (conchoidal fracture). It has a distinct sparkly or sugary appearance due to the recrystallized quartz grains.
Formation & geological history
Formed by the metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains and silica cement to fuse together into a dense, crystalline rock.
Uses & applications
Widely used in construction for wall cladding (as seen in the image), flooring, countertops, and as railway ballast. Also used as a source of silica for glass making and in various industrial abrasives.
Geological facts
Quartzite is so hard and dense that it will scratch glass and even steel. Unlike sandstone, which breaks around its individual grains, quartzite breaks through the grains because the rock is so thoroughly fused.
Field identification & locations
Identified in the field by its extreme hardness, vitreous luster, and lack of reaction to acid. It often appears as rugged ridges in mountain ranges due to its resistance to weathering and erosion.
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