Koa (Acacia koa) grows only in Hawaii. It is a very desirable tonewood, because of its striking beauty as much as it's tonal characteristics. Koa has a beautiful golden color, often with brown or black streaks. Even plain pieces sport a wonderfully lustrous sheen, but highly-figured curly koa has appears to be three dimensional.
To rosewood lovers, koa's tonality is not as impressive as its visual beauty. A koa guitar falls in the middle of the tonal spectrum along with mahogany and walnut. It has a bright clear voice with good sustain, but noticeably less bass than rosewood. If you like the crispness of mahogany with added woodiness and little more sustain, koa may be your ideal tonewood.