Ema Egg

Ema eggs are also known as seer stones, window quartz or dreamer's crystal.  They are naturally tumbled in a river, which is why they are frosted.  One side is cut and polished, creating a window or a face that sees into the stone.  Historically, they have been used for scrying.  

Others carry it as a pocket stone for the individual properties of the stone. 

Sizes range from 3/4" to 2".  Each stone is unique and may slightly vary from what is pictured.