If it looks like the black halibert in this picture, i think the original origin of it was an event on (thinks Atlantic) years ago, and also herd something about a bug were they could be looted in doom off something again years ago.
The most recent origin was from the changling dupe which flooded Uo with them.
The fact its on SP would make it worth more than other shards, but iv seen them anywere from 1-10mill but that was about about 2 years ago, havent seen one for sale in years now.