Can you get a sample to take home and test? Quartzite shouldn’t stain or etch. Marble will.

Whatever it is, the stone is gorgeous!

Pretty stone but I do not see the point of leathering a stone since a polished surface is easier to care for.

In this case it's not possible to tell just by looking at it. You have to test it.

http://usenaturalstone.com/definitive-guide-quartzite/

If you are dealing with an established local supplier with a good reputation, it probably is what they say it is. Look online for comments, complaints and recommendations for this particular company: in the world of the internet, it is easy to Google a company by name and find comments by customers.

When looking for countertops, I fell in love with one stone that turned out to be marble instead of quartzite, so I went to another company and picked out another "quartzite" that turned out to be dolomite (only slightly more durable than marble).

One quick check: google the name of the your stone. If most companies are calling the stone marble, it probably is marble. My google search for "Calacatta Chiarra" had most of the results saying it was Marble or "Soft Quartzite" (i.e. not quartzite). It could be two different stones with the same name, but the samples posted online look similar. I would definitely bring samples home and test it for hardness and it's ability to resist etching and staining. My mislabelled "quartzite" samples failed miserably (etching, staining and scratching) and I picked something else.

Only you can know if a marble can work for you in the kitchen. You may be able to be super diligent, but will your guests? Sealers can help, but you will also have to be diligent with that. You don't want to know you need to reseal because a stain develops.