About 30+ years ago we started using a wood we considered an Ebony substitute called Caviuna by one supplier. Later we saw the wood used elsewhere called Morado. Then again, called Pau Ferro and also Bolivian Rosewood. The common names now that is most used in these parts is either Morado of the fancy Brazillian name Pau Ferro. Pau=wood and Ferro=ferrite/iron aka Iron wood. One book I have says there are over 80 species called Iron wood. It's just a descriptive name for very hard wood, not a particular species. Most wood names are names, not species as well.
The wood I am referring to is a 'Machaerium' species and that is the actual name the wood is called when it enters the country,
'Machaerium Villosum'.
Have a look here;
http://www.kensmithbasses.com/woodpages/morado.html
Its weight is about 85% that of ebony but very stiff. Also, it is very stable and shrinks less in use making it an ideal substitute for Ebony FBs. The only draw back is the color being of various brown shades and never black IF that's a problem. I have seen a few DB FBs of this but only a few.