Quartzite

Hardness: 7 (Mohs scale), Color: Light tan, white, gray with greenish tints, Luster: Vitreous to waxy, Crystal Structure: Trigonal/Hexagonal (granular), Cleavage: None, Specific Gravity: 2.6 - 2.7

Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, causing the original quartz grains to recrystallize into an interlocking mosaic. Found in orogenic belts and regional metamorphic terrains.

Used in construction for road ballast, floor tiles, and wall coverings. High-purity quartzite is used in the glass industry and to produce silicon and ferrosilicon. Smaller decorative pieces are used as garden stones or lapidary material.

Quartzite is so durable that it can survive the erosion of the softer rocks around it, often forming the caps of hills and ridges. It is differentiate from sandstone because it breaks through the grains rather than around them.

Identify in the field by its extreme hardness (cannot be scratched by steel) and its granular, sugary texture. Often found in riverbeds as smooth pebbles due to its resistance to physical weathering.