Mesquite
"Mesquite (scientific name: Prosopis) wood is conceivably the most dimensionally stable of all woods in having equal radial and tangential shrinkage values of only 2%-3% and in having total volumetric shrinkage values of 4%-5%. Other fine woods such as oak, cherry, walnut, teak, mahogany and Indian rosewood have volumetric shrinkage values in the range of 8%-15%. The result of the low shrinkage value is that furniture made from mesquite will have less expansion and contraction when ambient humidity levels change, such as from summer to winter in northern regions. Thus, furniture will not crack and drawers will not stick with changing humidity levels." (P. Felker, et al, Grading mesquite lumber, Texas A&M- Kingsville 1994).
Texas Ebony
Texas Ebony is a member of the Legume family, Pithecellobrium flexicaule. It is very similar to Mesquite and is closely related. In the Mimosa family, the tree is shrubby and grows up to 60 feet tall, and three feet in diameter. It is rare, growing only in southern Texas and northern Mexico. The wood is extremely hard and dense, and very durable. A dark chocolate brown to black, with distinct striping in the grain, it polishes to a mirror shine. It takes frets extremely well and once dried properly it is extremely stable and won't warp with changes in humidity. Difficult to work and rare, but its extreme density (sinks in water), color, polish and stability are everything you could ask for in a fingerboard.