metamorphic
Quartzite
Quartzite (mostly SiO2)
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
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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.
