Gray hairs are indeed unusual, and not only because of their color. Gray hair is stiffer and more wiry than hair rich in pigment. Exactly why this is the case is not fully understood.
Gray hair has reduced levels of melanin, which is the pigment that gives hair and skin its color. Within the hair follicle, stem cells of melanocytes (the cells that produce melanin) and keratinocytes (cells found in the epidermis), sebaceous gland secretions, and numerous other factors interact to give hair its color and texture. With age, the level and activity of many of these factors declines, resulting not only in reduced pigmentation but also reductions of lipids and growth factors. The result is coarser and less manageable hair.