These ogres are for the Shaman Totemic armor quests. They ask for Dufrenite
to crush, powder, or grind. I think it's a bit of a stretch to expect it to
work for the diamond dust. What you get after giving them Dufrenite is one of
Crushed Dufrenite, Powdered Dufrenite, or Ground Dufrenite. If it was
possible to get Dufrenite Dust from them, I might be tempted to try diamonds,
but as it is I would not recommend it to anyone.

Finkin
18th Gnome Magician, Xegony

or,

Nizuk Kuzin
35th Troll Shaman, Innoruuk