title: How can I correctly uninstall gems from OSX's system ruby 1.8.x while using rbenv + different ruby version?
body: <p>I have <code>rbenv</code> and <code>ruby 2.1.0</code> installed currently and I want to move forward with any gems I install for this version of ruby.</p>
  
  <p>However I also have the system (OSX 10.9) default ruby (1.8.x) and I had previously installed some gems for that version. I can see them here:</p>
  
  <p><code>/Library/Ruby/Gems/1.8/gems</code></p>
  
  <p>I have no idea how to get <code>gem</code> to properly uninstall from the above dir so I can clean my machine up and reinstall newer versions of some of those gems for my <code>rbenv</code> managed newer version of ruby.</p>
  
  <p>For example, I had installed Compass and Sass for 1.8.x, I don't need Compass any longer and would like it removed from my machine and would like to upgrade Sass from 3.2 to 3.3 but have it run off ruby 2.1.0.</p>
  
  <p>Currently, <code>gem list</code> gives me only the currently installed gems for my active version of ruby set by <code>rbenv</code>, which makes total sense.</p>
  
  <p>So how can I run <code>gem uninstall &lt;old ruby 1.8.x gem&gt;</code> found at <code>/Library/Ruby/Gems/1.8/gems</code> ? </p>