When was it cut? How long did the log or stave sit with the bark on, outside, inside, in the weather, etc.? How, precisely, was it cared for from the time the tree was dropped? Is there any bug damage? Any other signs of degradation? Did you remove the bark? If so, when? Give us some history please.
Black locust is rot and bug resistant, but it isn't rot or bug proof. And the sapwood is less impervious than the heartwood. Some discoloration of the sapwood may or may not be indicative of the heartwood's condition, so it might, MIGHT be ok.
I just went through 5 logs of black locust that I cut about 4 years ago. I left them outside on a limestone driveway. The bark was loose and fell off. Figured the heartwood would probably be ok. Upon splitting them open, all sapwood was discolored and the heartwood was beginning to rot, with the beginnings of bugs, fungus, and about 70% discoloration. It seemed to follow the natural checks and voids down deeply into each log and spread out from there. Burned It all. I won't attempt a bow with 2nd rate wood.
