I've turned a few pieces of old growth heart pine. The wood was originally used for beams, flooring and other heavy or heavy use purposes in construction. It is the same group of species as current southern pines, but being old growth in virgin forests it grew much slower and the growth lines are very close together. With the slow growth and resulting concentration of pine tar it is very much as if it is naturally stabilized.
Probably every lot of old heart pine is different, depending on how dried out it has become, but what I turned was very hard and stable. It did not pull out fibers on the end grain. The finished turning was also on the boring side, old wood makes for a good story to tell, but not necessarily for an attractive pen.