I love finding surprises/anomalies with wood grain. I bet that will look pretty when finished. Try hitting it with a black light and see what it looks like. black locust is downright psychedelic in the black light.
I have some hazel with deep chocolate streaks in the center. It could be caused by anything from disease or damage to minerals in the soil. Just be sure to test the breakage on a piece before putting hours into a bow. Sometimes different can be bad with regard to the normal physical properties.