Unmistakably oak. The colour is straw/brown. The tangential grain (top picture) shows a characteristic ring porous, coarse, open grain. You can even faintly see the greyish dark brown medullary rays running left to right in this view.
The end grain pictures reveal the bands of open pores of spring growth alternating with dense summer growth. However, what seals it as oak on this wiew are the vertically running white ribbony medullary rays.
As to species, it could be an European oak such as Quercus patreae or Quercus robur, or one of the American oaks such as Quercus alba. It could be one of many of this type of oak, but the three I've mentioned are probably the most likely candidates.
It's certainly not a red oak as the end grain is too dense lacking the typical very open pores due to the lack of tyloses typical of the red oak varieties. It's also the wrong colour and not open grained enough. Anyway, they (red oaks) are native to the north American continent and not in great demand in Europe. Having said that, red oaks have been imported and planted in the UK, have adapted, and grow very successfully here. Slainte.
