metamorphic
Quartzite
Metamorphosed Sandstone (SiO2 - Silicon Dioxide)
Hardness: 7 on Mohs scale; Color: White, gray, pink, or light tan; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65
- Hardness
- 7 on Mohs scale
- Color
- White, gray, pink, or light tan
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: White, gray, pink, or light tan; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65
Formation & geological history
Formed through the intense heating and pressure of sandstone (metamorphism), usually during mountain-building events (orogeny) in tectonic plate boundaries. Most specimens date back to the Proterozoic or Paleozoic eras.
Uses & applications
Used as a crushed stone in road construction, railroad ballast, and as a decorative stone in landscaping. In its pure form, it is used to produce silica sand for glassmaking and industrial abrasives.
Geological facts
Quartzite is so hard that it will scratch glass and steel. It is more resistant to weathering than the original sandstone from which it formed, meaning it often forms the peaks of ridges and mountains.
Field identification & locations
Identify by its grainy, sandpaper-like surface that looks like sugar but feels smooth to the touch across individual grains. Unlike sandstone, it will break through the quartz grains rather than around them. Found globally in mountainous regions.
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