i'm in with the black locust crowd. Honey/yellow locust has much smoother bark, even on the trunk where it starts to get craggy, the high spots are flat, reddish, and not SO craggy. BL has deep cragg bark like an old poplar or cottonwood, but darker, and the color on that stave's heartwood is perfect. Black locust heartwood ranges from a dark yello-brown with an olive undertone, to an orange-brown with a muddy undertone, almost like dirty mulberry heartwood.
The UV thing is interesting, I think I had heard of it and forgotten. But, alternatively, you can smooth one side of that split with a scraper/sandpaper, wet it or slap a little clear finish on the spot, and get some light angling off it. BL usually has little striations crosswise in the rings and seems to have an internal golden luster. Mulberry just has minor, but pretty color variations running through it.
