We all tend to personalize our office. Pictures of families, hobbies, and random stuff end up taking over the odd corners of our desks. Geologists tend to collect rocks.
I'm not a big fan of rocks in general. I'm a dirt and contamination person. Sure, if I'm coring rock or I pick up something cool in the field, I'll take it along. But many times, the interesting rocks don't make it all the way to my office.
So I don't have a rock collection. What I do have is a drilling detritus graveyard.
It started when we (the driller) destroyed a roller bit (example from wikipedia below) in some particularly difficult terrain.
The driller chucked the bit in my direction and said "why don't you take it?"
So I did. I ended up as sort of a broken bit magpie. When something shears off or wears down to uselessness and can't be repaired, I'll take it back to the office as a sort of trophy of a difficult (and expensive!) day. The more mangled, the better.
The problem is that my collection makes for some heavy (and occasionally greasy) paperweights. Next time I move, maybe I'll donate my collection to the next enthusiastic newbie who chirps, "hey, what does this do?"