metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale (harder than glass). Color: Grey, white, or brownish/tan to reddish due to iron oxides. Luster: Vitreous to dull. Crystal structure: Hexagonal (microcrystalline). Cleavage: None (conchoidal fracture).
- Hardness
- 7 on Mohs scale (harder than glass)
- Color
- Grey, white, or brownish/tan to reddish due to iron oxides
- Luster
- Vitreous to dull
Identified More metamorphic →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 on Mohs scale (harder than glass). Color: Grey, white, or brownish/tan to reddish due to iron oxides. Luster: Vitreous to dull. Crystal structure: Hexagonal (microcrystalline). Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together into a dense, crystalline rock. This transition usually occurs during mountain-building events.
Uses & applications
Used as a decorative stone in architecture, as crushed stone for road construction and railway ballast, and occasionally as a source of silica for glass making.
Geological facts
Quartzite is so tough that it often outlasts the surrounding softer rocks, forming the resistant caps of many prominent mountain ridges. It can be distinguished from sandstone because when it breaks, the fracture passes through the quartz grains rather than around them.
Field identification & locations
Identify in the field by its extreme hardness (will readily scratch glass) and its granular, sugary texture. It is a common ridge-forming rock found globally in metamorphic belts such as the Appalachians or the Alps.
More like this
