A baseball card sold for more than $12 million at auction, making it both the most valuable sports card and the most expensive piece of sports memorabilia ever sold at auction. The Mickey Mantle baseball card from 1952 was graded a Mint+ 9.5 by Sportscard Guaranty Corporation, and was sold by Heritage Auctions for $12.6 million at 12:28 a.m. CST,…