The fabricator for my kitchen and vanity countertops will be making the floating sink for my powder room. I'd try contacting local fabricators to ask if they fabricate floating stone vanities/sinks.

I have no idea, but my thought is that because marble is so dense and heavy, floating it would require a very strong method of attaching it to the wall. I wouldn't think it's worth the trouble, but that's just me.

^^^^^ @Diana Bier Interiors, LLC - you're correct. If it's a large floating marble vanity and sink it will be heavy and require very strong brackets. I've decided that mine will not have a marble/stone sink - instead it will have an under-mounted sink (also, I feel like an actual marble/stone sink will be difficult to keep looking nice).

My vanity will be located within an alcove - 43" wide. It will have plenty of brackets to hold the weight of whatever stone I select (I may select quartzite) - each bracket is able to support 500 lbs:

FYI - a HUGE advantage to having a local fabricator construct the floating stone vanity allows me to select the exact slab that will be used. My fabricator does a lot of business - in addition to purchasing slabs from several suppliers in the area, he also imports many types of natural stone slabs (including some unique ones that he finds on his annual trips to various overseas locations). He has a HUGE grave yard filled with remnants - many that will work for the size I need (21" + 10-12" mitered apron with over 43" length) = keeps the material cost lower.