Visualruby install fail (win7)

I followed the instructions for installing visual ruby - install ruby
193 and glade, then in a ruby window typed ‘gem install visualruby’ and
got the following output which shows the gem install output, and what
happened when I typed vr.

I’m a complete noob in this area so it’s probably something very obvious
to the ‘knowledgeable ones’ but I’d appreciate some advice.

A preview of the output after I pasted it here was unreadable, so I’ve
put it in the file I’ve attached.

Visualruby install failed. info follows:

ERROR: Error installing visualruby:
ERROR: Failed to build gem native extension.

    /usr/bin/ruby1.9.1 extconf.rb

/usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in require': cannot load such file -- mkmf (LoadError) from /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:inrequire’
from extconf.rb:1:in `’

Gem files will remain installed in /var/lib/gems/1.9.1/gems/json-1.8.2
for inspection.
Results logged to

running Mint 17 64bit computer i5 processor

Any advice ?
Jim S

Nort sure I did this correctly.