metamorphic
Quartzite (or Milky Quartz pebble)
Quartzite (Metamorphosed Sandstone) / Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale); Color: White, light gray, or tan; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None; Specific gravity: 2.65.
- Hardness
- 7 (Mohs scale)
- Color
- White, light gray, or tan
- 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 (Mohs scale); Color: White, light gray, or tan; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None; Specific gravity: 2.65.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. Geological age can range from Precambrian to Cenozoic depending on location.
Uses & applications
Used widely in construction as crushed stone for road bases, railway ballast, and as a raw material for glass manufacturing. Highly durable for landscaping.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the tops of ridges and mountains because it resists weathering better than surrounding rocks. It can be distinguished from marble because it will not react with acid.
Field identification & locations
Identify in the field by its ability to scratch glass and its grainy, sandpaper-like texture that has been 'welded' into a smooth, hard mass. Commonly found in metamorphic belts and as river-worn pebbles.
More like this
