Go After him NOW
Comet-
Post everything you have on this seller on this thread. The Forum users are very good at scaring up information, and you will also get the benefit of their experience.
Honestly, I believe there is no intention to ship your block, and I doubt the seller will respond on this forum. Therefore you must shift into attack mode. Gather your information, print copies of your emails and any pictures, locate the authorities (including attorney general) in the seller's city and state. The USPS MO opens the door to a mail fraud claim.
Its been a month which doesnt seem like a long time- What I would find concerning is that the seller was invited here to clear his name and responded with silence.
That suggests he is not interested in clearing his name-and thats all the answer you need to know.
Scorp