metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: can vary from white/grey to brownish-red due to iron oxide; Luster: vitreous to dull; Crystal structure: hexagonal crystal system but typically presents as a granular mass; Cleavage: none, breaks with a conchoidal or splintery fracture.
- Hardness
- 7 on Mohs scale
- Color
- can vary from white/grey to brownish-red due to iron oxide
- 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: can vary from white/grey to brownish-red due to iron oxide; Luster: vitreous to dull; Crystal structure: hexagonal crystal system but typically presents as a granular mass; Cleavage: none, breaks with a conchoidal or splintery 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. These are found in mountain ranges globally and can range from hundreds of millions to billions of years old.
Uses & applications
Used extensively in construction as crushed stone for road base or railway ballast. High-purity quartzite is used to produce glass, ferrosilicon, and silicon metal. It is also used as a decorative stone in architecture and landscaping.
Geological facts
Quartzite is so tough that it often outlasts other rocks during erosion, remaining as resistant ridges or 'monadnocks' on the landscape. Unlike sandstone which breaks around individual grains, quartzite fractures through the grains themselves.
Field identification & locations
Identify in the field by its superior hardness (cannot be scratched by a steel nail) and grainy, crystalline texture that lacks the distinct layering of some other metamorphic rocks. It is commonly found in older mountain belts like the Appalachians or the Alps. For collectors, look for specimens with unique coloration or surface weathering.
More like this
