Ebonizing other high-tannin wood (like oak, walnut, or cherry) will also get you a black/near black finish without dye/stain.
Plus, the science of it is kinda cool! Rusty metal (iron oxide) + vinegar (acetic acid) + time ==> iron acetate, which reacts with the tannin in wood and turns it black. You can optionally pre-treat the wood with a strong black tea to add even more tannins to the wood prior to treatment.
One can use the same concoction (called “vinegaroon” in leatherworking circles) on veg-tan leather to blacken it.
Reacts quickly, penetrates deeply, doesn’t rub off. Cool stuff.