Quartzite

Physical Properties

Hardness: 7 (Mohs scale), Color: White to light gray, Luster: Vitreous to sugary, Crystal Structure: Hexagonal crystals (now interlocking grains), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together into a dense, solid rock. This specimen shows a granoblastic texture (sugary appearance).

Uses & Applications

Used in construction for road ballast and flooring, as a source for silica in glass manufacturing, and as decorative stone or countertops due to its durability.

Geological Facts

Quartzite is so tough that it often survives intense weathering better than surrounding rocks, forming the caps of ridges and mountains. It will scratch glass easily, unlike marble which it often resembles.

Field Identification & Locations

Identify in the field by its hardness (cannot be scratched by a steel blade) and its sugary, sparkling texture where individual quartz grains have fused. Found globally in fold mountain belts.

Identified on: 5/15/2026

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