I have noticed this and not sure if its intentional, but it seems there are shadowstones that are catalysts, and ones that arent, is this intentional or not?
Unintentional, if you know where the ones not marked are coming from please post them here.
I found some of the unmarked ones in the laboratoryium? (old efua observatory imp quest??)
That is where I was finding some as well. So looks like the loot table might need tweaking, if I hear of where any others are coming from will post, not sure what I should do with the ones I currently have though.