Oldred: My first encounter with fumes from torch-cutting galvanized was bad enough that nobody had to warn me to avoid it after that. That was over 25 years ago and I can still remember that feeling.
The black pipe in the upper part of that photo is new. The rusty pipe at the bottom has been laying around waiting for this job for many years. I suppose it's possible it was galvanized at some time, which would fit powerrodsmike's and matt167's comments, but it shows no evidence of galvanizing. It's evenly rusty all over and inside and out. I did my welding outside so that could explain not smelling anything or noticing strange smoke. The green stuff is mainly on the rusty pipe side of the weld, suggesting that pipe is where it comes from.
What about pipes from oil drilling? There are a few oil wells in the region and since I don't know where the pipe came from, it's possible it came from one of those. Do they do anything that gets chromium on or in a pipe? These don't look worn out, though, and I've heard that pipes discarded from oil operations are thin and brittle.
It just bugs me to not know what it is and where it came from.