I posted the comment about the butcher block solid Maple, it was on the thread originated by Redkiwi, and the subject was shelf material. This type of Maple can be ordered from McMaster Carr. I have tried the solid Granite block, typically used as a machine tool stand. The Granite blocks are available from machine tool supplies, but my results with them proved to be overly bright and ringing, much like the stone itself sounds when struck with a hard object. Testing with particle board and various layers of damping material surrounding the Granite, proved only to move the resonances around in the frequency range, rather that eliminate them. I settled on the solid maple and am pleased with its neutral, clean and uniform treatment of the music. I can only suggest that those of you with the time and energy, to try as well, and report here what you find. I would not be surprised that the results will vary with equipment, acoustic environment and room construction materials. Best luck.
