You'll probably have to use an external one. Apple is not Blu-ray friendly. (That was their choice, as a former HD-DVD backer.)
There's not even Blu-ray authoring software that I know of. So why put a Blu-ray burner in a Mac?
Edit: Encore CS5, maybe?
Lacie makes this for $350:
http://www.amazon.com/gp/product/B00...SIN=B003D4OXCQ
Or instead of $350,
- Buy the Pioneer for $95:
http://www.amazon.com/gp/product/B00...SIN=B004ILKH64
- And gut the $95 Lacie DVD external:
http://www.amazon.com/gp/product/B00...SIN=B001P5C9S0
So ~$200 for the external Pioneer drive. That's what I'd do, if I really needed Blu-ray on a Mac tower.
Trying to cram a BD-R into a drive-unfriendly Mac just isn't going to be a pleasant experience.