Tufa casting is an old technique developed by the Navajos in the late 1800s. A design is carved into tufa stone, a porous, volcanic pumice found naturally on Navajo land. Molten silver is poured into the mold. Molds typically only last one casting and then are no longer usable. The texture of the tufa stone is distinctive and remains on the finished piece unless polished. Tufa cast pieces are one-of-a-kind works of art.