Black walnut, is from the walnut trees that grow wild, mainly throughout the eastern US. It is usually referred to as just "walnut." The word "black" does not mean it is darker. The other less common types of walnut are Claro walnut, which is darker than black walnut. These are the walnut trees that are clutivated for English walnuts, or the kind of walnuts you buy in the store. Claro walnut is usually more desireable than black walnut as it is usually more figured, a bit darker and more expensive.
European walnut is lighter in color and probably less figured. Peruvian walnut is very dark brown and much softer than other walnuts, and somewhat figureless.
One thing about commercially cut, kiln dried black walnut is: it is typically steamed which among other things, darkens the sapwood and results in a more uniform and usually darker and so etimes grayish color. Many woodworkers (including me) prefer air dried walnut, which I think results in a warmer mid brown color with more interesting lighter and darker color patterns. Black walnut is not soft, but not real hard like cherry, oak, or hard maple, but is hard enough to be durable. It does not splinter easily like oak, so is condusive to carving. I personnaly just love the stuff. Matt...