Best Platter Material

In the 'old days' when TT was the only game in town, Dual had a 2-piece platter, either half would ring like a bell when struck, but together were nearly inert. Resonant frequency of each piece was carefully chosen.

For a budget job it was very good and well executed.

If I were building a 100% cost no-object TT, I'd investigate Carbon. I don't know if some of the more exotic forms...Graphene or Buckeyballs are available in large enough quantities yet. It may obviate the need for anti-static measures.

Boston Audio graphite mat works really well with Nottingham Spacedeck. Its platter is made of..I have no idea, but it's quite heavy and not glass or acrylic or delrin. Some sort of alloy.

I think the alumimum/lead sandwich of the VPI TNT made an excellent platter, but the platter interface with the record is a different story. for that I use and recommend Delrin, which is also my second place choice for the entire platter.
You are asking for two different things. One, which material makes the best platter and two, which material interfaces best with the record. The answer to those questions are likely two different materials, as I stated above.

Living voice mystic mat is very good.

Does all the things that my copper top on the TW Raven AC-3 does except removes the slight edge that can afflict the copper top.