metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, but can be pink or reddish due to iron oxides; Luster: Vitreous (glassy) to dull; Crystal structure: Trigonal (granular); Cleavage: None, breaks with a conchoidal or uneven fracture; Specific gravity: 2.6 to 2.7.
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous (glassy) 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, but can be pink or reddish due to iron oxides; Luster: Vitreous (glassy) to dull; Crystal structure: Trigonal (granular); Cleavage: None, breaks with a conchoidal or uneven fracture; Specific gravity: 2.6 to 2.7.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. Under intense heat and pressure, the individual quartz grains recrystallize and fuse together into a dense, interlocking network of crystals.
Uses & applications
Used in the construction industry for crushed stone, road ballast, and roofing granules. Because of its hardness and resistance to weathering, it is used for floor tiles, stairs, and countertops. High-purity quartzite is used to produce silica sand for glassmaking.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock layers, forming spectacular ridges and mountain peaks. Unlike sandstone, which breaks around the grains, quartzite breaks right through the quartz grains because the bonds between them are so strong.
Field identification & locations
Identify it by its extreme hardness (cannot be scratched by a steel knife) and its grainy, sugary appearance on a fresh break. It is commonly found in mountain belts worldwide, such as the Appalachian Mountains in the USA or the Alps in Europe.
More like this
