1.we have very early cases of using corals as part of necklace (beijing museum have han dynasty corals, but i do think it goes early then that, if we look into burals)

2. fact that pemaraka is ming - makes it something relatively new, we have corals in Tang dynasty statues inlays

3. corals always demanded higher price then red cornelian, in any market including today.

4. idea that something expensive (red corals) been used to replace something cheap (red cornnelian) is naive

Have nice day