Gary, I've never seen a black one before and think that it's cool that it is still on the tree. The leaves on our oak tree a very different than the ones you have here and our acorns start out green then turn brown. Very interesting. :)
@novab Thank you Nova! We have several different varieties of oak trees here in the South and their acorns are often very different, some quite large! I thank you so much of your comments!!