This is an AMAZING handmade gray clay studio art pottery piece.  The mug is made of a light gray clay and is the perfect thickness.  It is a beautiful blue color that lightens to a gray at the base and on the inside.  There are darker gray (almost black) areas in the glaze as well.  It can hold about 12 ounces of beverage.  This mug is 4 inches tall and 3.5 inches in diameter at the rim.  It is handmade and was bought from the artist in the 1990s.