Handcrafted by Thomas Filippini in Richmond, VA.  Sterling Silver and Turquoise Tufa Ring. Tufa casting is a traditional Native American jewelry-making technique that uses a porous volcanic ash rock called tufa stone to create molds for casting silver or gold. The artist carves a design into the tufa stone, creating a mold into which molten metal is poured. The porous nature of tufa gives the finished piece a unique texture and often results in a one-of-a-kind piece due to the mold usually breaking after a single use. SIZE 7.5