Where is ruby stored on mac?

You can find your answer by running one of the following commands:

 which ruby
 whereis ruby 
 type -P ruby

You can get the path to the local executable with

$ which ruby

the rvm rubies are in your rvm directory, which I believe is ~/.rvm/rubies (I use rbenv so not sure about the details)

The which command should pickup whatever shims/other magic RVM is using to set your shell ruby