Is this a porcelain TILE counter?

A really good fabricator who has considerable experience with

porcelain is key.

thanks, its a 12cm porcelain slab counter but of course when you cut out the sink opening, the veins will not go through so I just wonder if there are any special ideas people have around that edge

A 12cm slab would be almost 5 inches thick. Surely not.

It's 1/2" must have converted wrong!

You must mean 12mm, almost 1/2".

Match the sink to the tile body color, and with the edge polished, you should have a virtually invisible seam. As in, use one of the Blanco Silgranites. The metallic gray is often close.