Well - I stretched it out longer than I had intended. I threw everything I could think of at this piece of Madre Perla, or Mother of Pearl Quartzite. Oil, grapefruit, lemon and lime juices, sat a martini glass on it, raked it with a fork, after two hours I washed it with a wash cloth and dried it. Also left a can of tomatoes on it for an hour with the metal bottom right in the middle of all this acid. Not a mark on it. After that I took a cut lemon and left it cut side down for another hour and a half and I also took a paper towel with gritty salt and rubbed at it for a minute. I took my sharp butcher knife and ran it across the sample with a decent amount of pressure and still not one single mark. I don't know what to tell you. Based on these experiments I would definitely put this product in my kitchen as my counter top.
One thing I should mention is that natural quartzite does have a mesh backing and one of my kitchen fabricators said it will have a tendency to be a bit more brittle so I wouldn't stand on it or smash at it with a mallet.
It's possible that this particular stone is harder than other quartzite products.
I wish I had a definitive answer for you and will explore this further as I wouldn't want to specify a product that won't stand the test of time.
If I am able to find out anything more I will definitely keep you all in the loop.
It would be great if someone from the Marble Institute of America would respond to this thread with information which would help you all.
Q