a friend of mines mother gave me a few suckers from her blueberry “tree” in new hampshire. it fruited in its second year. the fruit are jet black and shiny with no bloom on them. i mean they are ripe aronia black. taste is very complex. sweeter than any blueberry I’ve ever eaten and i find it has a raspberry undertones. very interesting. the original ‘‘tree’’ is nearly 10ft and about 6ft wide and is very old. his parents are in their late 80’s and it was there when they bought the house… she has her other son pick it with a ladder for her. they usually get about 10 gallons from the one bush! its a naturalized blueberry to that area. I’ve heard of similar blueberries growing near water in some areas of M.I and southern maine as well. anyone ever hear of big high bushes like this? berries are medium size and flesh is even blue on them. our native bilberries look like this but don’t grow nearly as big as this one does.
Here’s an old post that reminded me of.Yours almost sounds like a Rabbiteye or a hybrid.bb
Could it be a huckleberry?
Edit: looking up huckleberries and seeing there’s a lot more species of them than blueberries. Apparently the seeds give it away if it’s a blueberry or huckleberry, blueberries have lots of soft seeds, huckleberry have 10 hard seeds.
the seeds are soft like a blueberry. and seeing I’m at z3b/4a i don’t think huckleberries grow this far north. the bush is only a foot tall now but time will tell if the berries get bigger. they are identical to the wild bilberries here but bilberries rarely get higher than a few ft. and are sparse producers. maybe a hybrid of the 2? also the pics I’ve seen of wild high bushes , the berries are all powder light blue.
A picture would help.
ill try and post some.
Very cool either way.
I know of a farm (woods is more accurate) that has 8 to 10 foot blueberry bushes…and the berries aren’t much bigger than elderberry fruits. Very tasty, but take forever to pick a mess.
But the fruits are nearly black…definitely darker than typical blueberries.
(This same farm has one or more producing native chestnut trees also.)
Sounds like a ‘tree’ I’d like to try rooting a cutting from sometime. 
I saw 7 foot tall black fruited highbush blueberries growing near Emporia Virginia about 40 years ago. Is it possible this is a black fruited highbush? Agree that the height is unusual.
these arevfairly small as well but my buddy told me they get to a medium size like the size of a large pea once the bush gets bigger. once the plant gets established i can help you out with a cutting or 2. 
the taste is a lot like a serviceberry but with some stronger raspberryish under tones.
Guess I ought to get busy and ‘practice’ on rooting blueberry cuttings then!
(I’ve been told cinnamon helps with rooting…may try that.)
Did you have any luck with the ‘autumn olives’? I am considering taking some cuttings this week and trying to root them.
I have a blueberry called “Blue Ridge”…it was selected in the wild in NC. More tasty and more hardy. Small fruit compared to most commercial varieties. I believe Rubel is such a variety? I have not grown that one.
I am guessing your mystery blueberry is simply a wild highbush selected by somebody years ago for some traits they were impressed with at the time.
i stuck a half doz. northland blueberry cuttings in the ground near the mother plant and 3 are growing. thats surprising as we are in a severe drought and they only got watered when i watered the mother. i also had luck with some carmine jewel and juliet cherries doing this. guess my clay soil is good for something. shared them with my inlaws and neighbors.
I had opportunity some dozen or so years ago to observe propagation by cuttings of blueberries in Ocala Florida. An I’ve bought plants where the little cell pack is still obvious, meaning they likely were stuck as cuttings, but possibly came form a test tube.
I have rooted many things on an experimental basis…often losing them somewhere between successful rooting and getting through a full year growth.
i think it helps i stick them early in the spring like late April as soon as i see bare soil… many weeks before their parents start to leaf out. the roots have time to form. i also limit top growth to only 1 bud. don’t know if it makes a difference in success but so far has worked for me.