[nickdothutton]

Originally I had planned to pursue geology as a career, and studied it at college. In those days there was still a significant element of the course which concerned hand specimens. Mostly rocks and minerals, but also an impressive display of different crude oils from around the world. High or low sulphur, viscosity, density. Uncapping the small tubes would stink up the whole room pretty quickly.

[HPsquared]

I think a lot of that strong smell is the mercaptans (organosulfur compounds) which are very pungent. Funnily enough that's what gets added back in to natural gas so people can smell if there is a leak.

[mr_toad]

Probably hydrogen sulphide, the active ingredient in stink bombs.