Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: Gray, white, or light tan; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Specific gravity: approx. 2.6

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together, creating a very dense and durable rock.

Uses & Applications

Used extensively in construction as road ballast, railway track ballast, flooring, roofing tiles, and as a decorative stone in landscaping. High-purity quartzite is used to produce silica sand for glassmaking.

Geological Facts

Quartzite is so hard and tough that it will break through the quartz grains rather than around them (unlike sandstone). It is often more resistant to weathering than the surrounding rock, frequently forming ridges and hilltops.

Field Identification & Locations

Identify in the field by its hardness (it will easily scratch glass) and its sugary, crystalline texture that lacks the distinct foliation layers found in rocks like slate or gneiss. Commonly found in folded mountain ranges.

Identified on: 4/19/2026

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