Error in the countertop, allegedly natural…

This is an enclosed diamond…

Honestly: natural product. Come up with a nice story about it.

...

If such countertops also exist without a large, conspicuous spot in the middle, I am of the opinion that those are more like "B-grade" and the countertops without such conspicuous "outliers" are "A-grade." Did your sample have a large white spot somewhere? Or was the countertop reduced in price? It would actually bother me too. As a guest, I would probably always rub against it because I would think it’s a stain. I hope for an exchange for you; otherwise, I would put something on it that does not disturb the design.

I would negotiate a price reduction and then enhance the small white spot with a permanent marker in gray or black using dots.

...Price reduction without argument and then messing around on it with a marker?
Wow...

Good spot for a throw-through... ;)

I totally understand the OP, it would annoy me every day and I also think it significantly disrupts the appearance. Of course, it is a natural product, but the deviation from the rest is quite noticeable. I have never seen anything like that to this extent, and many people around me have black granite. No idea if you just have to accept it like that. For a first assessment, maybe ask the consumer advice center, if they even advise on something like this.