This is a piece of Chrome Diopside from the Merlani Hills in Arusha, Tanzania. That is the same mine that Tanzanite comes from! It has some beige colored crystals on there that may be colorless Tanzanite. It gets its green color from the inclusion of Chromium, hence the name Chrome Diopside.
This piece measures approximately 3.6cm long x 1.6cm wide x 2.4cm tall. It comes with the acrylic stand that it is on and a display card that lists the mineral name and locale