Although called blue, the colour is a slaty or drab tone.
The skins that are not perfectly white are dyed jet black, dark or light smoke, violet-blue, blue-grey, and also in imitation of the drab shades of the natural blue.
Has a close dark drab underwool with yellowish grizzly, grey, regular and coarse top hair.
The bark, very dark externally, is an excellent tanning substance; the inner layers form the quercitron of commerce, used by dyers for communicating to fabrics various tints of yellow, and, with iron salts, yielding a series of brown and drab hues; the colouring property depends on a crystalline principle called quercitrin, of which it should contain about 8%.
In the XIIth Dynasty a hard thin drab ware was common, like the modern qulleh water flasks.