Jade rectangle not sure of value

Got this jade rectangle from a buddy of mine, both of us didnt know the value and were wondering how much something like this could be worth if its real jade. I know it came from someone who has money so its got to be worth something is what i am thinking.

my question is How much could this be worth and if it has worth how might i go about selling it? 

What is it? 

The size fits in the palm of my hand