metamorphic

Quartzite

Quartzite (chiefly SiO2)

AI-generated identification · may be incorrect

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

Identified May 26, 2026More metamorphic →

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Physical properties

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.