metamorphic
Quartzite
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: reddish-brown with grey/white interior; Luster: vitreous to dull; Crystal structure: trigonal (granular microcrystalline); Cleavage: none, breaks with a conchoidal or irregular fracture; Specific gravity: 2.63-2.65.
- Hardness
- 7 on Mohs scale
- Color
- reddish-brown with grey/white interior
- 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: reddish-brown with grey/white interior; Luster: vitreous to dull; Crystal structure: trigonal (granular microcrystalline); Cleavage: none, breaks with a conchoidal or irregular fracture; Specific gravity: 2.63-2.65.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse together. The reddish hue is often caused by iron oxide (hematite) staining.
Uses & applications
Used in construction as road ballast, railway ballast, and building stone. Due to its hardness, it is also used as an abrasive and in the glass-making industry when highly pure.
Geological facts
Quartzite is so tough that it often survives intense weathering and erosion long after surrounding rocks have crumbled away. In many mountain ranges, the highest peaks are capped with durable quartzite.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and its sugary, granular texture on fresh break surfaces. Commonly found in folded mountain belts and ancient shield areas.
More like this
