You often get really acidic brews from speciality roasted beans because they err on the side of not pushing through the second crack and serve earlier in the roasted life before some of the gas has escaped. Were the beans really black and oily or have a more browny tinge?
This was many years ago so my memory of such details is quite fuzzy, but to the best of my recollection they were not oily. I remember being a little surprised by that.
