Quartzite is a tough, hard, fine-grained metamorphic rock. If the quartzite is made of pure quartz it is white, but it may have yellowish or reddish colour if it contains iron minerals. If you use a magnifier you may be able to see the grains of sand from which it is made.
Quartzite breaks through the grains and not around them like sandstone. Don’t confuse quartzite with marble, which is much softer. Quartzite is very hard and will easily scratch glass.
How is it formed?
Quartzite is formed from the metamorphism of sandstone.