Tufa-casting is an ancient technique that uses large blocks of sandstone, which have been mined from the Hopi reservation in Arizona. The blocks are cut into chunks and smoothed with a brick into two matching pieces. Designs are carved into the stone with a variety of tools. The carved pieces are paired, blackened with a torch and sealed, allowing for an opening at the top through which molten silver or gold is poured. Once the metal is cool, the stone is taken apart, revealing the newly formed piece. The tufa stone leaves an organic earthen texture to the final pieces. Often, stamp work techniques with natural inlay materials and a variety of stones and shell are applied. This technique allows only one unique piece per mold.