metamorphic
Quartzite (Orthoquartzite)
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or reddish-brown (from iron oxidation); Luster: Vitreous to dull; Crystal structure: Non-foliated, interlocking quartz grains; Cleavage: None (conchoidal to uneven fracture); Specific gravity: 2.6 - 2.7.
- 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, gray, or reddish-brown (from iron oxidation); Luster: Vitreous to dull; Crystal structure: Non-foliated, interlocking quartz grains; Cleavage: None (conchoidal to uneven fracture); Specific gravity: 2.6 - 2.7.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure causes the original quartz grains and silica cement to recrystallize into a dense, interlocking mosaic of quartz crystals. Most major deposits date back to the Proterozoic or Paleozoic eras.
Uses & applications
Extensively used as crushed stone in road construction, railway ballast, and as a raw material for glass and ceramics. Highly decorative varieties are used for countertops, wall cladding, and as decorative stone in landscaping.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than around them, unlike sandstone. It is often the capstone of ridges because it is extremely resistant to chemical and physical weathering.
Field identification & locations
Identify in the field by its sugary texture and extreme hardness (it will easily scratch glass and stainless steel). It can be distinguished from marble because it will not fizz when exposed to dilute hydrochloric acid. It is commonly found in mountainous regions or ancient cratons like the Appalachians or the Canadian Shield.
More like this
