I think you mean the darker, smaller streaks, yes? I’m assuming they are made on purpose when the quartz is made - to mimic the natural variations in natural marble. Did you purchase the quartz from a small size sample? This can happen when you see the full size of your countertop in place. But I think it’s meant to be.

Look at another slab for similar dark marks. If you don't see any send a picture to the manufacturer for analysis by their customer service techs. Always take photos of your slabs before fabrication. Those three similar oblong dark spots aren't something the manufacturer would likely include in the design. Everything is planned. Not like natural stone. There shouldn't be random negative unrelated marks.

I think it is pretty standard to have "contaminants" in the quartz. A friend has a dark blob that looks like a dead bug ... I try to wipe it every time I am there!

Were I your estone manufacturer or your fabricator, I'd tell you those are within the specified standards. It's a variation, not contamination. This is contamination:

This customer has grown to lover her bright red spot; she would not let me remove it.

All very pretty. The black spots look intentional to me