Vibration Isolation for equipment using granite?

I am not arguing that a solid stone rack takes away the benefit of good chassis feet. On the contrary, it can be argued the the better the rack, the better the (best) feet can perform. I am only saying that stock feet will perform better too (for example, on my MA-1 amps, or Aesthetix Io preamp). The rack itself offers much more stability and mass, compared to what I had before. My overall impression is that superior stability and mass translate to authority and precision in the sound. 

Before, I had a VPI record player needing a lot of tweaks to perform its best, including a Bright star sand box. And even some air in a bike tube. Endless tweaking. I changed to a Hanss T-30 player with adjustable "maglev" suspension. This stands direct on the top rack stone shelf. No looking back. 

Strictly off topic, but it does not harm that some granite looks beautiful as well. Here is larvikite, my rack resembles pictures C and D. 

https://www.researchgate.net/figure/Larvikite-subtypes-polished-slabs-7-x-7-cm-a-Kjerringvik-b-Bergan-c-Klastad_fig7_267806277

Mass stores vibration [energy] and thus does NOT dampen it. 

What you want is tuned dampeners (eg springs) on a light and stiff platform (or screwed in, such as isoAcoustic Gaias on a speaker, with the proper version of the Gaias depending on the mass of the speaker).

Tuned meaning matched properly to the load. You obviously need a lot stiffer dampers for a 120 lbs speaker vs. a 50 lbs amplifier vs. a 10 lbs turntable. 

I don't know if using granit with amps or TT  can improve sound but it definitely improved the sound when used under my Dynaudio Contour Legacy even if they have cast iron bottom integrated plates. The bass is tighter among others. Used 3/4 inch. Worth testing on other components.

Constrained layer is the way to go; I use an HRS platform on a big Minus K isolation platform for a very heavy high mass table (Kuzma XL plus Airline arm). 

I'm not sure one stone over another is the answer.  You can probably make what is necessary if you know what you are doing- I went for commercially available solutions -- works a charm.