Vesuvianite

Vesuvianite is named after Mt. Vesuvius in Italy where it was first discovered by a German mineralogist named Abraham Werner. 

It was found in limestone blocks ejected from the mountain.  While the mineral that makes up Vesuvianite (idocrase) is quite common, finding it in Gem quality is quite rare!  

It has a hardness of  6.5 on the Mohs Hardness Scale.