Clinkerbelle

With a set of flimsy gauze wings glued to his back, this was a small troll who attempted to establish the hitherto unknown tradition of a Troll Tooth Fairy.

It is thought that he had heard that humans had a cultural practice whereby teeth could be exchanged for small coin, and he had given this what must have been postgraduate-level creative thought about how it could be applied to trolls, whose teeth are of course made of diamond. Being able to exchange small coin for multi-carat jewellery-grade diamond which could then be resold to such as Vortin for not inconsiderable sums seemed like good economic sense, and thus a scam was born.

Alas, it only lasted as long as it took for him to be hauled in by the Watch whose troll officers were unanimous in dere not being such a fing as a Toof Fairy. But you can't fault a good idea.

Geology

Clinker is the residue left in the firebox of a coal-fired boiler.