What is .GEM file?
Package that may contain Ruby programs and libraries; saved in a self-contained format called a "gem;" can be installed using the RubyGems package manager application included with the Ruby software.
Ruby GEM files can be installed using the "gem install GEMNAME [options]" command. You may also use the "gem list -r -d" command to list the gems installed on a network.
Recommended Software Programs to open .GEM file