Ack chew ally, you cannot control the very low frequency seismic type vibrations with materials such as mahgister just mentioned no matter how exotic the materials or in what combination.
I am very happy with just good for the moment.... Perfect this is not.... And you are right for the difference between damping and isolation for sure....
But all is a question of trade-off/cost.... My sandwiches solution cost peanuts and are very good without being perfect.... Vibrations controls is one embeddings only.... The money spared will be invested better by someone who use my low cost solution in the electrical grid embedding and mostly in the acoustical embeddings... The audible effects of a rightfully treated room exceed any other changes....Then a good isolation and damping solution like mine even if not perfect for sure suffice to most people.... :)
I will add your spring solution one day to my sandwiches when i will be in the obligation to recreate my audio system, selling my house....After that without being perfect my sandwiches+springs would be very good indeed....Except for isolating my audio system for Yellowstone eruption for sure or fire truck passing near by my sandwiches are good enough for now.....
I will leave perfection search in audio to you, myself i will be happy with a good audio only and a good woman only....I wish you also the perfect one tough....
:)