Hickory diseased?

Hi
Last winter a rather large hickory tree came down across my driveway. I have a nice slice of this tree I was going to use for mallets and handles. When I finally got around to opening it up I see the outer wood looks like the hickory I know but the inner wood is very dark brown (see photo) My question: is the brown inner wood some kind of disease? Does it contribute to any loss in strength of a billet?

Thanks
Don
Don.Carolan@comcast.net
Attachment 455052

hickory is multi colored naturally, I would though keep as much of the dark wood out of what ever you are making as far as handles go. Hickory wood flooring is nice to have the color changes if you like contrast.