Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: white to creamy beige with slight pinkish/iron staining; Luster: vitreous to dull; Crystal structure: Hexagonal (as individual sand grains now fused); 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 from tectonic activity, the individual quartz grains recrystallize and fuse into a solid, interlocking network. It can be found in mountain ranges and ancient shields.

Uses & Applications

Used primarily in construction for crushed stone (road ballast), dimension stone for countertops and tiles, and as a source of silica in glass manufacturing. Some pure varieties are used in landscaping.

Geological Facts

Quartzite is so hard that it can scratch a glass bottle and even a steel knife blade. In many areas, quartzite ridges remain standing while softer rocks around them erode away, creating prominent topological features.

Field Identification & Locations

Identify in the field by its hardness (it will scratch glass) and its sugary, grainy texture on fresh breaks. Unlike marble, it will not fizz with acid. Common in metamorphic belts and can be found as river cobbles far from its source.

Identified on: 4/24/2026

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