Barro Negro Skull MugBeautiful barro negro skull mugs have arrived, just in time for day of the dead! Check out the bones handle of this mug. Barro negro is a type of pottery only found in San Bartolo Coyotepec, Oaxaca and crafted using traditional methods. The black color comes from the clay itself, enhanced during the firing process. 3. 5 x 6. 5 x 3. 75. Approximate measurements, all mugs are made by hand and will differ slightly in presentation.