Unable to uninstall gems from command line if gem initially installed from RM

Hi.  I'm having trouble uninstalling gems that were installed through RM (5.4.1).  According to the documentation that I looked through (http://www.jetbrains.com/ruby/webhelp/installing-and-uninstalling-gems.html), when I used the command line to uninstall a gem, I get the message that the gem is not installed.   However, when I issue the gem list command, I can see the gem in the list.  Since I use rvm to install/manage my ruby modules, I navigated to the .rvm/gems/<rubyversion/gems directory, and noticed the gem that was installed through RM is not listed.

How can I uninstall a gem which was installed through RM?