Why is parts of my skin highly reflective?

Im a black male my skin color is almost like that of a penny. On various areas of my body (Lats, around my underarms, shoulders, triceps, upper back very lower back, and butt area) are highly reflective to light (sun and artificial). I Generally don't lotion these areas only my hands face arms and legs. It is not excessive oil. People think it is completely beautiful but I would like some explanation as to why this happens.