If it is a piece of diamond rough, then there is an entirely different pricing structure involved. You would have to take it to a diamond cutter to have it evaluated.
To answer your question…. it is worth whatever someone is willing to pay you for it and what you are willing to accept for it… the price lies somewhere in between.

best thing to do is go to a jeweler and let them appraise it, that will give the correct amount of what its worth

you forgot to say the cut and if it’s a VVS1 or a VVS2.
but i’m going to estimate that you could buy an identical one in perfect shape for about $9000, but i’m not sure what yours is worth. but you’d still have to get it appraised to really know.