Stringreen, I respect your opinion based on the totality of your contributions here, which is why I asked to know more about the Terrastones. Skepticism is usually not inappropriate in this hobby, but because you like the Terrastones, I would make the effort to learn more about them.
I made some footers for my slate-plinth Lenco in the following way: I purchased small-size cans of Mandarin Orange slices in water, three of them. To the bottom of each I attached some Black Diamond carbon fiber conical footers using double-sided tape. (I had a set given to me.) The bottom surface of the slate plinth is placed againt the "top" side of each of the 3 cans, and that's it. I had noted that the anti-skate weight of my Dynavector DV505 tonearm would readily start swinging whenever I walked past the turntable, even though it is sitting on a very large and heavy Adona rack, on one of their damped granite shelves. The can-footers have nearly completely damped out that phenomenon. I think it would be even better if I were to insert some spacers, so that the bottom surface of the slate plinth engages only the top surface of each can, not including the raised edge around the circumference of the top. Total cost: about $6 plus the use of the Black Diamond cones. Any such conical feet would do the job, IMO.
Theory: the Mandarin Orange slices in water provide a sink to absorb and dissipate vibrational energy entering from below. The orange slices serve to break up any regular wave motion of the water which might otherwise transmit to the plinth. (By the way, it looks more professional if you remove the labels from the cans, could be even more expensive looking if you paint the cans black, white, or silver.)
