As ypg has already written. Create a defect notice with a deadline for remedy.
Can you at least prove exactly what you ordered?
Is there a protocol for the final order? Or an order confirmation?
Could the black scratches not also originate from incorrect handling or contamination?
Did you report the defects while they were still on site? Otherwise, each subcontractor blames the other.
Refuse acceptance until the defect is remedied. Withhold part of the outstanding invoice amount.