Yep, you're going to have to support the weight in some fashion with an apron at the edge or recessed to hide the support. The material is not self supporting.

You might be able to get away with thick plywood to support the top held back from the edge but the wood turn on end like an apron is so much stronger.

Is the island built and in place yet? Better would have been an "oak clad 4 or 6 inch depth wall running middle of the 50 inch length. It looks too weighted right side anyway. Yes, you would still have plenty of knee room, not to mention a less "leggy look.

Most islands have no more than 12 /15 overhang for stools

Take your fabricator’s advice. See “millworkman”’s comment.

I am a fabricator ... and an engineer. you need a structure supporting the 50" extension. plywood is inadequate. A pair of horizontal beams running from the cabinet to the posts and another beam post to post is the correct way to do it. The beams can be set back 8 or 10" from the edge so they won't interfere with leg room and won't even be visible from close by. Your quartzite is expensive stone, take the fabricators advice.

To me no need for that huge overhang with no cabinets under it a much better plan would be a wider island with a 12" overhang on one side , more stools and a much nicer supprt for the counter and no legs but maybe a nice waterfall end in what appears to be a contemporary space .

Thank you you all for your quick advice, I really appreciate it. My kitchen is too narrow to do seating on only one side. Also I should have mentioned in my original post that I will have an apron of support around edge that carpenter is adding, but it is not steel, and not sure if it is covering the whole area. Thank you all for bringing up these important thoughts, I will share with fabricator!

Yes, take the fabricators advice. You need good support under the slab.

"I will have an apron of support around edge that carpenter is adding, but it is not steel, and not sure if it is covering the whole area."

Anything less than steel is not going to be adequate for that large an overhang.

We have a 12” overhang and our contractor put steel supports underneath. Suggestions … Taj Mahal quartzite which is a light colored stone. We went to many stone places before picking Taj Mahal and found that there was a variety of slabs out there, some much darker than others or with a lot more gray in them. We were able to find 2 in sequence that we loved with the help of a great tile gal. I didn’t realize how much having them in sequence mattered until looking at 2 from opposite ends of the same bunch and seeing how much the color can vary and how they didn’t go together well. As far as staining … it looks like new so far, and we’ve had it 6 months. It needs to be sealed, but that wasn’t tough to do. We did the leather finish as it was suggested that it showed less scratches, etc. than going with polished and I couldn’t be happier with that choice.

The quartzite can be installed in this application when supported properly, so in that sense the fabricator is wrong.

Hello, I am not a fabricator or design professional but thought I would share my experience with a quartzite countertop. Just under 2 years ago we chose quartzite (white Macabus”) over quartz for our new kitchen countertops. While we are very happy with the visual aesthetic of the stone, we were surprised by its tendency to absorb moisture. If a wet cloth or sponge is left on counter for any amount of time it would leave a spot. Not a stain, mind you, just a dark spot that will eventually evaporate over a couple of hours. We have sealed the countertops at least 3 times to try and discourage this from happening but have come to realize this is the nature of the stone. We have also been told that different types of quartzite may have different absorption rates so if the spotting would be an issue for you, you may look into those slabs with a minimum absorption rate. Best of luck!