metamorphic
Quartzite
Quartzite (chiefly SiO2)
Hardness: 7 on Mohs scale; Color: Reddish-brown, maroon, or purple (due to iron oxide); Luster: Vitreous to dull; Crystal structure: Non-foliated, interlocking quartz crystals; Cleavage: None (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- Reddish-brown, maroon, or purple (due to iron oxide)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-brown, maroon, or purple (due to iron oxide); Luster: Vitreous to dull; Crystal structure: Non-foliated, interlocking quartz crystals; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically in orogenic belts. Many reddish/maroon varieties are associated with Precambrian or Paleozoic formations.
Uses & applications
Used as a decorative stone, in construction as crushed stone or railway ballast, and occasionally for lapidary work or as hearthstones.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock, forming resistant ridges. It is harder than steel and can scratch glass easily.
Field identification & locations
Identify by its extreme hardness, sugar-like crystalline texture on fresh breaks, and its inability to react with acid. Commonly found in riverbeds or glacial tills across North America.
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