Wow, I have never seen a sink seam like that with quartz.

Is this a 2cm or 3 cm quartz. Did they laminate something onto the edge?

3 cm quartz. I don't know if it's laminate or just whatever seal was used, but there's clearly a transition between the top and that edge around the sink. And I'm guessing the dirt has gotten under that finished top because I can't get it out at all.

Do you know the brand of the quartz?

My quartz sinks (bathrooms) have no seam at the edge. They just cut the sink hole in the quartz and then polish the cut edges. No seam to separate or collect dirt.

I have used Cambria, Pental, Caesarstone and Radianz quartz brands and none had a seam at the sink edge.

That has every indication of being a polyester miter/lamination that''s failing due to the water at the sink.

Drop the sink, cut it out, profile, polish, and reinstall the sink.

Oof. That's a lot more complex than I was hoping it would be. It's a new construction home that was completed in January 2022. Do you think we have a legitimate complaint to make with the builder/installers?

" Do you think we have a legitimate complaint to make with the builder/installers? "

What was the builder warranty? Typical is a year.

Are those striations in the sink cutout? Can they be felt? If so, that's probably from worn cutting tools and lack of process to remove them. Unacceptable.

" Do you think we have a legitimate complaint to make with the builder/installers?"

It depends upon what the line is. If it's failing adhesive as I suspect, it's going to continue to separate. As it separates, it's going to become contaminated, ugly, and unsanitary. In a few years, long after the warranty expires, it's going to fall off.

Something is off here. I would be worried about what that is covering. You should NOT need a laminated strip.

is it possible that there is a very thin layer of quartz over particle board or something? What does it look like underneath - solid quartz?

I agree with Just Janni. If the quartz is 3 cm why the need to have a laminated strip on the edge?

Here is my 3 cm Cambria quartz edge around a bathroom sink. They just cut the sink hole and polished the edge ... there is no need for a seam at the edge.