A Kevin Costner quote from the July 2012 issue of Cowboys and Indians magazine:
C & I: So how does a 21st-century guy immerse himself in a 19th century character like Devil?
Costner: I start working with black powder. I start working with how to load those guns. I start looking at costumes; I start looking at beards. And I start looking at cadence, how people talked back then. I read letters written by people back then. [Laughs] In this case, I needed to find the right beard and the right hat. And the right pipe. I had to make the decision between this little corncob pipe and this little almond one - and I took the almond one.
This doesn't answer the question of what type of pipe it is, but does indicate it was a conscious decision on Costner's and his producer's part.