Look up the "geology" threads by karin_mt. She is a geologist and writes for the stone industry. She has many simple tests that you can do to the corner of a slab or a sample piece, to determine if it is a real quartzite or dolomite/marble.

You might be told that a slab is a soft quartzite. That does not exist and it is a dolomite/marble!

Also a slab could be hard like a quartzite, but porous like a marble, and those slabs need to sealed regularly so they don't stain and etch.

There is a lot of information on the forums, you just need to spend a bit of time searching and reading.

Thank you so much!