Quartzite

Physical Properties

Hardness: 7 on Mohs scale. Color: White to light grey. Luster: Vitreous to dull. Crystal Structure: Hexagonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.7.

Formation & Geological History

Formed through the metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. This typically occurs at convergent plate boundaries.

Uses & Applications

Used in construction as crushed stone for road beds, in the glass industry as a source of silica, and as decorative stone for counter tops and landscaping.

Geological Facts

Quartzite is so tough that it often survives erosion better than almost any other rock, frequently forming the tops of ridges and mountains. It is harder than steel and will easily scratch a glass bottle.

Field Identification & Locations

Identify in the field by its hardness (it will scratch glass) and its sugary texture on broken surfaces. It is commonly found in mountain ranges and ancient continental shields worldwide.

Identified on: 5/13/2026

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