metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: light grey to white, Luster: vitreous to grainy matte, Structure: granular (crystalline), Cleavage: none (conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: light grey to white, Luster: vitreous to grainy matte, Structure: granular (crystalline), Cleavage: none (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz sandstone under intense heat and pressure. This specimen shows signs of being water-worn into a cobble/pebble shape.
Uses & applications
Used as railway ballast, in construction as crushed stone, for making bricks, and occasionally as a decorative landscape stone.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock, forming resistant ridges and hills. It reacts differently to tools than sandstone because it breaks through the grains rather than around them.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and its crystalline, sugary texture. Common in ancient shields of continents and mountain belts.
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