There are many sub-species of Swartzia, or what is sometimes called "ironwood," (trade names: izerhardt, wamara and bania.) This wood is very heavy and dense, often quite dark as the name implies, though some sub-species' boards are lighter in color. These woods vary widely; it seems that every example is a different sub-species. I am told by David Persram that there are, in fact, more than 20 closely related species. The challenge has been to find the most beautiful boards that have sufficient stiffness to accept the thinning required to achieve a good, light weight. (Some species are useless; I have discarded many varieties and boards.) The best examples for bow making of these species are quite stiff and not overly heavy; classical and modern bows require that the tip and frog be higher, the stick diameter reduced and the cambre adjusted. Other examples are very similar to the finest Pernambuco. These and other related species are among the finest bow material I have found. They also have the advantage of requiring only a few years aging to be stable. Tonally, these woods can be superb. Rarely seen in bows made before 1780.
*One common sub-species, Swartzia leiocalycina, is, in my opinion, a superior wood, as fine for modern design bows as the best rare pernambuco. See my gold-mounted Peccatte model viola bow pictured on this site as an example.