If you have the wood cut- here's another way to tell them apart. First, honey locust tends to have a wide band of white sapwood, maybe 2-3 inches, whereas black locust has a much narrower band of sapwood- 1/2 to 1 inch at the most. Then the color of the heartwood of honey locust varies from orange to peach to pink, or even a blend of all those colors. Black locust has a distinct greenish-yellow color.
Now I don't know where you are at in your tree I.D. but there is one more possibility. There is also the Kentucky Coffee Bean Tree, also called just coffee bean cause it grows in other states besides Kentucky. The wood ,however, is nearly identical to honey locust, and is often these two woods are mixed at a saw mill.