Howdy! Not a cue maker but have experience with black locust. If it is dry forget about turning or cutting it. Had to replace several fence rows on the farm. Posts were old black Locust posts sawed on the property by my grandfather. I wanted to save the posts and just install new Woven Wire. If you could get a staple out it didn't matter you would never get another staple driven into the post. Ended up cutting the wire in between each post. Tried sawing one and it destroyed chainsaw chain. Slip chain and skid steer were the only option. pulled out the posts and put in new ones. I could only imagine trying to turn that on a lathe it better be a horse.
I have heard black locust is hard, but never used it that I can remember. I have heard of some Methodist preachers having hard sermons before, but never heard your saying before.