Black Walnut is highly prized for its dark-colored true heartwood, which is a rich purplish-brown shade to a chocolate-brown tint. The wood is heavy, hard, and strong, easily worked and has an attractive grain. Iowa is a leading producer of walnut timber which is the single most important tree in terms of price per tree. Walnut wood has historically been used for gunstocks, furniture, flooring, coffins, and a variety of other woodworking products. It is so valuable that so-called "Walnut Rustlers" have been known to harvest it illegally by posing as forestry officials, cutting trees during the night, and even using helicopters to take them away quickly; such over harvesting has greatly reduced its numbers and range since colonial times. (More on Walnut Trees .)