http://www.theguardian.com/world/2015/feb/26/isis-fighters-destroy-ancient-artefacts-mosul-museum-iraq - this is what im talking about
It's a little hard to see from video which stuff destroyed were originals and which were replicas. The winged bulls were original, while many of the statues were not. I'm sorry I can't help more than that.
They destroyed many artifacts which are beyond worth. How do you place a value on statues from a civilization from 5000 years ago? However, slowly chipping away pieces of stone with a chisel and jackhammer is about as exciting as watching paint dry. So, the video shows them mostly pushing over plaster replicas, which make a big crash and shatter for dramatic effect. They DID really destroy ancient artifacts of incalculable worth. But they wanted to make a good propaganda film, too.