Marble to place speakers on?

The best marble under speakers is the cheapest marble - ie. the marble with the most impurity. The impurity stops the marble ringing. Is is dolomite that is the impurity? I cannot recall - but I have tried different marble and the sound is better with the cheaper stuff.

Where do you guys get this marble? Just 3 days ago I put some ceramic tile 1/4"X 12"X 18" under my speakers.It was very cheap ($2ea.) and it was all I could find that would fit.I have my speakers spikes almost all the way into the speakers.They are out about 1/4" I hear no ringing or anything else other than deeper and tighter bass.I still would like to try some marble if I can find it.

david: most cities of any size have suppliers and fabricators of stone countertops, floors, etc. i have purchased over the years several "scrap" pieces of marble and granite from a supplier in denver. i've not used these under speakers, but i know from experience that pieces of marble of the "correct" size for most speakers' footprints are readily available. the prices will vary rather dramatically depending on the color and "purity" of the marble you want. as redkewi sez, tho, you shouldn't go for the purest stuff, e.g., white carrera. your choice of stone, and its relative purity, will likely be dictated by the color you want. the last piece of marble i bought was "green empress," which i used as a top insert on a muse model 18 sub; it was beautiful but i wouldn't choose it to mate with my current speakers. good hunting. -kelly

If I do bolt the speakers to the marble, am I doing away with spikes all togather hence adding mobility by sliding?

I agree with the above comments/suggestions. At a prior home where I had a pier/beam foundation, I used marble slabs (but did not bolt the speakers to them) that I found at a rock shop while traveling through Arkansas. The results were impressive (ditto previous comments). I am currently in a home with a slab foundation and have spikes that go through the carpet and pad straight to the foundation. The results a very similar. I still have the marble but it is being used for other applications (in the backyard). Bottom line: Use spikes if you have concrete under your speakers. If not, plan a vacation! :-)