There are Thousands of Free WordPress themes available on the Internet for Free. Many themes are created as Child Theme and some make clone themes. If you will search in Google about Free WordPress theme then you will get Thousands of Links of Different Sites for it.
Recently I was search for a New Free theme for one of my Blog when Suddenly I found a theme which Look like Mashable and the name of the Theme is WP Mash Thirteen. MP Mash Thirteen is a Child theme of TwentyThirteen and is Powered by TwitterBootstrap 3.0. It is not the Exact Clone of the Mashable theme but you will have a Feel of Mashable Theme.
You can convert your Blog to a Clean and Beautiful design like Mashable. The theme works only with TwentyThirteen parent theme and you can add a lots of creative Work to its Content.
The Theme is Responsive and Works Perfectly on any Mobile device or Tablet.