Wool does not mold
Wool insulates, even when wet

Wool fibers have a waxy coating

Because the surface of the wool fibers with its waxy coating is water repellent, spills can be removed before they can penetrate the wool. Even if a stain is not removed immediately, wool is less likely to suffer permanent color damage than other natural or synthetic fabrics. Wool also absorbs much less sand or dust from the ground than other fabrics. The best way to clean a sand stain or the like in your Russian wool socks is to simply wipe with a dry brush, as wool releases soil and the like quickly.