marble or granite slab under floorstanders?


Anyone have advice on whether to go with marble or granite ?

I'm looking for a custom size made, where's the best place to buy from? Thanks
mrkoven
Clearthinker, doesn't matter how much mass you put under a turntable. It will still pick up all kinds of crap. The only adequate solution is a well suspended turntable (SOTA, BASIS, SME, Dohmann) or a MinusK platform. Electron microscopes directly on a concrete floor are a nightmare. This is usually what MinusK platforms are used for. 
As for other equipment? You can theorize that tubes need isolation although I have never seen proof of that. Otherwise it is just another profit making scam perpetrated on audiophiles. The only reasons to put anything under a loudspeaker are to keep the spikes from marring the floor or to get them up to the right height.