I wonder if the surface of the clay dry lake bed contains a mineral called kaolin? Kaolinite is a clay.It is a sweet, earth, usually white mineral (dioctahedral phyllosilicate clay), produced by chemical weathering of aluminum silicates such as feldspar. In many parts of the world is pink-orange-red by iron oxide, which is a clear hue.It oxide is widely used as a replacement for talc.It also used as a lubricant.It is This will gives bright shiny smooth appearance. If the kaolinite is the leaching of clay when wet with water or a submerged surface to become very smart!
Sailing Stones