Quartzite
“Sandstone reforged”
Metamorphic
Quartzite forms when quartz-rich sandstone is metamorphosed by intense heat and pressure, fusing the individual sand grains into an incredibly hard, durable rock. Unlike sandstone, quartzite fractures through the grains rather than around them.
Composition
quartz (dominant), muscovite, feldspar
Where Found
Sioux Quartzite (South Dakota, USA), Table Mountain (South Africa), Scotland, Brazil
Mohs Hardness
7
Fun Fact
Quartzite is so hard and resistant to weathering that it often forms the ridgelines and summits of mountain ranges long after softer surrounding rocks have eroded away.
Test Your Knowledge
Why is quartzite rarely used as a decorative building stone despite its beauty and hardness?
Related Specimens
Want to identify rocks yourself?