Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: typically white to gray, but pink or reddish due to iron oxide; Luster: vitreous to dull; Crystal structure: hexagonal (internal micro-structure); Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.7.

Formation & Geological History

Formed from the metamorphism of quartz sandstone under high heat and pressure. This process causes the individual quartz grains to recrystallize and fuse into a dense, interlocking matrix. It is found in mountain-building zones or Precambrian shields.

Uses & Applications

Used in construction as ballast, flooring, and wall coverings; crushed for use in road construction; used in industry as a source of silica for glass and silicon metal; occasionally used as a gemstone when color is vibrant (like Strawberry Quartzite).

Geological Facts

Quartzite is so tough that it often outlasts other rocks in the field, frequently forming the tops of large ridges and mountains. It is harder than steel and can easily scratch glass.

Field Identification & Locations

Identify by its extreme hardness and grainy, 'sugary' texture. Unlike sandstone, quartzite will break through the quartz grains rather than around them. It is commonly found in riverbeds as rounded cobbles or in craggy mountain outcrops.

Identified on: 4/13/2026

Mode: Standard