metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, often with yellow or reddish tints due to iron impurities; Luster: vitreous to dull; Crystal structure: hexagonal (internal/microcrystalline); Granular texture; Extremely durable.
- Hardness
- 7 on Mohs scale
- 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; Color: typically white to gray, often with yellow or reddish tints due to iron impurities; Luster: vitreous to dull; Crystal structure: hexagonal (internal/microcrystalline); Granular texture; Extremely durable.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together, erasing the original sand texture.
Uses & applications
Used as crushed stone for road construction, railway ballast, and building stone. High-purity quartzite is used to produce silica for glassmaking and silicon industrial products. Polished varieties are used for countertops and flooring.
Geological facts
Quartzite is so hard and dense that it will break through the quartz grains themselves rather than around them, which is a key distinction from its parent rock, sandstone. It is often more resistant to weathering than the surrounding rock, frequently forming ridges and hilltops.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and its grainy, sugary appearance on a fresh break. It is ubiquitous in mountainous regions and riverbeds.
More like this
