metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale. Color: White, gray, or tan with iron staining. Luster: Vitreous to dull. Crystal structure: Hexagonal/trigonal. Specific gravity: 2.6-2.7. Cleavage: Indistinct/Conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Color
- White, gray, or tan with iron staining
- Luster
- Vitreous to dull
Identified More metamorphic →
Explore Quartzite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 on Mohs scale. Color: White, gray, or tan with iron staining. Luster: Vitreous to dull. Crystal structure: Hexagonal/trigonal. Specific gravity: 2.6-2.7. Cleavage: Indistinct/Conchoidal fracture.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. Under intense heat and pressure, the sand grains recrystallize and fuse together into a dense, crystalline rock. Most often found in orogenic (mountain-building) belts.
Uses & applications
Used in construction as road ballast, gravel, and dimension stone for flooring or countertops. High-purity quartzite is used to produce ferrosilicon, industrial silica sand, and silicon metal.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks; it frequently forms the caps of ridges and mountains because it resists weathering so effectively.
Field identification & locations
Identify in the field by its grainy, sugary texture and extreme hardness (it will easily scratch glass). Unlike limestone, it will not fizz in contact with hydrochloric acid. Commonly found in mountainous regions or as rounded river cobbles.
More like this
