metamorphic

Quartzite

Quartzite (mostly SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: White to light grey with translucent patches, Luster: Vitreous to waxy, Crystal Structure: Hexagonal (microcrystalline), Specific Gravity: 2.6 - 2.8

Identified July 15, 2026More metamorphic →

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Physical properties

Hardness: 7 (Mohs scale), Color: White to light grey with translucent patches, Luster: Vitreous to waxy, Crystal Structure: Hexagonal (microcrystalline), Specific Gravity: 2.6 - 2.8

Formation & geological history

Derived from quartz-rich sandstone through intense heat and pressure (metamorphism) within the Earth's crust, often associated with orogenic (mountain-building) zones.

Uses & applications

Used as a decorative stone, in construction as crushed stone or road ballast, and as a source of silica for glass manufacturing.

Geological facts

Quartzite is so hard and chemically resistant that it often forms the caprock or ridges in mountain ranges because it resists erosion better than the rocks around it.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by steel) and its grainy, granular look which resembles sandpaper but feels smooth if water-worn. Common in riverbeds and on beaches near mountainous regions.