So my mom (the green thumb of the family) uprooted our old raspberry plant in the spring and transfered it to a different plot of soil in a different area of our backyard altogether. Today, while doing some work out there, she discovered that about half of our raspberries that had grown turned black.
We did a bit of research but to no avail as to how half of them could grow in black on the same plant; yes, I know that black raspberries themselves are their own species, but these grew unexpectedly without any known intervention.
They are safe to eat, and taste a bit more tart than normal raspberries, and are approximately the same size.
If anyone has any sort of idea why this has happened, it would be cool to find out how this happened.

Just to clarify.. you had a bush that you have grown for years and know the berries are red. You dug up that bush and planted it somewhere else in your yard that you know for certain to never have grown raspberries at all. The following summer, the raspberries on that plant ripened to half red and half black. Correct?