i found this from a guitar woodworking blog
"from what Todd (exotic wood brokers) told me, Asia ebony is similar to maccasar, but with some green in it, and turns a little muddy with an oil finish.
maccasar ebony is black, brown, and sometimes has some gray in it. Makes a very nice looking fretboard.
Gaboon is black ebony, and very hard/durible (as is most ebony)
Madagascar ebony, from what I've read (and please correct me if I'm wrong) is the blackest ebony out there, even more so than Gaboon (which sometimes has a few brown marks in it).
Hope that helps, and I'm going to be using a gaboon board on the project I'm working on now."
and here is some more info
www.homestratosphere.com
"from what Todd (exotic wood brokers) told me, Asia ebony is similar to maccasar, but with some green in it, and turns a little muddy with an oil finish.
maccasar ebony is black, brown, and sometimes has some gray in it. Makes a very nice looking fretboard.
Gaboon is black ebony, and very hard/durible (as is most ebony)
Madagascar ebony, from what I've read (and please correct me if I'm wrong) is the blackest ebony out there, even more so than Gaboon (which sometimes has a few brown marks in it).
Hope that helps, and I'm going to be using a gaboon board on the project I'm working on now."
and here is some more info

11 Different Types of Ebony Wood (Diospyros crassiflora)
Quicklist: Types of Ebony Wood Ceylon ebony African ebony Gaboon ebony Macassar ebony Pale moon ebony Coromandel ebony Mauritius ebony Mun ebony Myrtle ebony Queensland ebony Brazilian ebony Below we explain each type in more
