Marble or Granite shelfs in a hifi rack?

Stone is a terrible choice for Hi Fi racks, you would get better sound with cardboard and save money

I have had terrific success with thick granite, particularly
in combination with other isolation devices. I've also
tried the 4" in thick maple which I feel is even better.

To take the subject admittedly but interestingly off-topic for a sec, I once bought an unusual gift of a windchime made from shards of a particular kind of obsidian (natural volcanic glass) that forms in 'fingers'. Dangle these pieces from monofilament and they ring like bells, with a very pleasing overtones structure.

Anyway, although I have not experimented with this myself, many audiophiles and manufacturers seem to prefer one of manufactured granite or marble substitutes that are used in kitchen countertops, such as Fountainhead (hope I got that name right?). Presumably these are fabricated using bonding resins that act as damping agents.

At one time I had four slabs of 3 inch machined Granite and used them under amps, preamp and turntable. After experimenting with them (damping) in every possible way, I sold them. Could never completely eliminate the signature they imparted into the music.

Next I tried Neuance shelves, then 2 inch marine plywood shelves laminated with decorative finish, finally settling on 3" solid maple butcher block. I had the top and face covered with Westinghouse brand laminate in a semi flat gray color.

The Maple butcher block probably has a signature as well, it's just more natural sounding in my system. Perhaps trial and error is required for each person to get it right.

I just put in the Lack shelf I got at Ikea. Two 4" dia. brass discs are under the CDP and one brass disc on top. The Lack shelf is supported but 6 tiny brass spikes which have "o-ring" under them. The 6 tiny spikes then fit into the shelf holes of my Sound Organisation rack. The o-rings space the spikes from the steel shelf frame.

Trying to find small differences irritate me (at least tonight) but my initial impressions are:
- Lower frequencies are more articulate.
- Hall ambience is more audible.
- There are some strange and very unmusical resonances. Meaning some instruments have strange harmonics that aren't at all natural.

So does not seem to be a clear win-win situation. Maple sounds like a good idea. I think the goal is for NATURAL resonances - if you're going to have any.