Hórin, a Zhélruka Dwarf, claims rivers and streams can be panned to learn what is hidden under stone.
'Did you know, kízinek, that river and stream hold secrets to what lies hidden under stone?
'Do you not believe me? Take these panning things and see for yourself! You will not find the fabled realm of Thafar-gathol, but then, if you are not an utter drak, you may find something of value or use.
'Three rivers you will find here, or so the old tales tell: Greylin, Forest, and Heath. Go then, and see what you can find.'
The Greylin, Forest, and Heath Rivers can all be found in Ered Mithrin.
You should pan for precious minerals at all three rivers.
You should return to Hórin in Skarháld with the minerals you have panned.
You should sift through the contents of your panning bag in a rinsing cask, found in Skarháld.
You should bring the mithril flake to Hórin in Skarháld.