Black clay, better known as Barro Negro, comes from the town of San Bartolo Coyotepec in Oaxaca. These exquisite pieces ,which are only made in this region of Oaxaca, receive their beautiful black finish through the process of polishing the surface with a quartz stone. This compresses and smooths the surface which in addition to the lower firing temperature for an extended time results in a finish which is unique to these pieces and gives them their natural luster.