Granite surface plate

I use 3 x granite block samples as feet
for my
turntable. (They are about 4" x 4" x
1.5")
I decouple the plinth from the blocks
with
brass compression rings on their side.
See
my system pics. This way there is no
granite ringing but there is excellent
focus over butcher block.

I don't recommend this.
I have one from a machine shop and it really sounded bright and shrill.
I use a 3" thick maple block and I'm very happy with the warm clean sound wood brings to the table.

A simple way to dampen ringing is to apply a constrained layer damper onto the horizontal support surface/shelf.
The one I found to give excellent audible improvement is from Machina Dynamica: VibraBlock Constrained Layer Damper.

Responding to the mention above where brass compression springs have been used,
The same Machina Dynamica can supply "cryogenically treated high-performance hardened steel compression springs"
cleverly named "Cryo Baby Promethean Mini Isolators."

These may be placed against the rigid flat bottom of a component to support the component which is resting upon a horizontal surface. Whether this horizontal surface is granite or wood may be a matter of what sounds best; I prefer wood.

Next place the VibraBlock constrained layer damper onto your chosen shelf.
I prefer what I hear with this damper placed onto a supporting shelf for a component, rather then placing a damper directly on top of a component.

If granite is 3 inches thick it will not ring unless you hit it with a ball peen hammer. So just don't hit it with a hammer whilst music is playing.

I haven't tried the ball peen hammer test. I plan to use a thick maple butcher block next to the granite. The table will rest on three Stillpoint cones pointy side up.

The table, an original VPI Aries Extended,seems to really benefit from as much isolation and as solid surface as possible. Seems like every small change is audible.