metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: tan to creamy white with iron staining, Luster: Vitreous to dull, Crystal structure: Trigonal (microcrystalline), Cleavage: Indistinct (conchoidal fracture), Specific gravity: 2.6-2.7
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 (Mohs scale), Color: tan to creamy white with iron staining, Luster: Vitreous to dull, Crystal structure: Trigonal (microcrystalline), Cleavage: Indistinct (conchoidal fracture), Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. Under intense heat and pressure, original quartz sand grains recrystallize and fuse together into a dense, hard rock. Primarily Proterozoic to Paleozoic in age.
Uses & applications
Used in construction as crushed stone for road ballast, as a decorative building stone, and historically as a source of silica for glass manufacturing.
Geological facts
Quartzite is so hard that it will scratch glass and even high-quality steel. Unlike sandstone, which breaks around its individual grains, quartzite breaks across its grains due to its interlocking crystalline structure.
Field identification & locations
Identify in the field by its extreme hardness and sugary, crystalline texture on fresh surfaces. Often found in mountain ranges or Shield areas where tectonic activity has occurred.
