Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: typically white to gray but often yellow, tan, or green due to impurities; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7.

Formation & Geological History

Formed through the metamorphism of quartz sandstone by intense heat and pressure, typically during mountain-building events (orogeny). Grounded quartz grains recrystallize and fuse together.

Uses & Applications

Used as a decorative stone in landscaping, a functional material in road construction (railway ballast), and for kitchen countertops. Historically used for making stone tools due to its hardness.

Geological Facts

Quartzite is so hard and chemically resistant that it often forms the ridges and peaks of mountain ranges because it resists erosion better than the surrounding rock.

Field Identification & Locations

Identify in the field by its hardness (it will scratch glass) and its sugary texture. Unlike sandstone, quartzite fractures through the grains rather than around them. Common in riverbeds and mountainous glacial deposits.

Identified on: 4/27/2026

Mode: Standard