Epoxy granite or mineral casting

[Jonathan]

For economy I'm guessing the trick is to use as much aggregate as possible ensuring it is adequately embedded/wetted (IYKWIM) in the binding (resin?) material.

Yes that's the general idea - I've read the thread on CNCzone and a lot of it is discussing what threshold is too much aggregate since they want to save money on epoxy.

A lot depends on what you want to use it for. The thread on CNCzone is so long because they are trying to find a mixture capable of providing a stable accurate surface which will directly support linear guides. If you're only using it to fill gaps in a casting for damping, or if you embed pieces of metal and fasteners which can subsequently be machined then clearly the requirements aren't so strict...