I know this is an old thread, but it remains a relevant topic. For the record, the "Candy's Dirt" article that Debb linked to is bunk. It's not the resin that etches, it's the stone. I've written to them and asked them to correct that misinformation, but never got a response.
I wrote an article to help people sort out real quartzite from the imposters. It's not hard to tell them apart, but you do have to test the stone - don't take people's word for it! Oh, and note there is no such thing as 'soft quartzite.' That's a total oxymoron and is misleading.
http://usenaturalstone.com/definitive-guide-quartzite/
Q
article about quartz vs quartzite
Q