They are pretty damn heavy.
Interesting tidbit... Here in this page, Naga Sadow thrusts his blade effortlessly into the table that is the centerpiece of the Sith Lord council chamber.
Later on, Ludo Kressh breaks his blade on the very same surface, only striking it sideways.
I wonder... was this because of raw strength used, or perhaps it was more Force than physical hitting that made it shatter like glass?