Mesquite, Pecan, black Walnut, and Mesquite (yes, I know I said it twice).
Mr. Doyle, if you don't mind me asking, from where do you source your African Blackwood? I've purchased about 50 blocks in 1.5x1.5 x 6-18 in the last 6 months and not one, regardless of grade, has been darker than macassar ebony. Its all from different suppliers and each has told me that their pieces were select grade or better but not ONE has been above average. Zero out of 50 have been black.
I try to buy mine at shows if I can. But it's getting tougher. And the stuff I'm getting lately has been less black than I like. I went to a show in the spring and a dealer there had a whole bunch of blocks rough cut and not stabilized (which is how I prefer my blackwood). I bought every block he had.
Before that I bought some online and I don't remember where but I just googled african blackwood and looked around for the darkest stuff I can find. If I can't see the exact piece I'm buing, I don't buy it.
I know that wasn't very helpful in locating you a source, but as you said, it's getting harder all the time and I have bought any since that show in April.