Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: typically white to gray, but iron staining often produces reddish-brown or yellowish hues as seen here; Luster: Vitreous to dull; Structure: Granular, non-foliated; Cleavage: None (breaks with conchoidal or uneven fracture).

Formation & Geological History

Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together, creating an extremely durable rock. This specimen shows significant weathering and iron oxide staining from environmental exposure.

Uses & Applications

Used heavily in construction for crushed stone, road ballast, and railway ballast. Due to its resistance to weathering, it is also used as a decorative building stone, in countertops, and as industrial silica source for glass making.

Geological Facts

Quartzite is so tough that it often outlasts the surrounding rocks that contain it, forming prominent ridges or mountain peaks. Unlike sandstone, when you break quartzite, it breaks through the grains rather than around them.

Field Identification & Locations

Identify in the field by its extreme hardness (cannot be scratched by a steel blade) and its grainy, crystalline texture that lacks the layers or pores of original sandstone. Found globally in ancient mountain belts.

Identified on: 5/15/2026

Mode: Standard