Tasmanian Blackwood, also called Australian Blackwood, is comparable to Walnut in tone, workability and density. It is used extensively in boat building and furiniture and has of late found popularity among a number of guitar builders.
Tasmaina Blackwood is indigenous to eastern Autralia and is similar in appearance to Koa with less golden reddish coloration and is sometimes used in place of Koa. If you're purchasing a Koa guitar, make sure it is truly Koa and not Tasmanian Blackwood, as Koa is considerably more rare and expensive.