Made of Silquar, a unique ceramic material which forms a protective blanket around any stone or jewel while adjacent metal parts are being soldered or heated. Resists temperatures up to 2000¬_F (1093¬_C), Odorless, non-toxic, and easy to use. Good for hundreds of jobs, because it is reusable. Comes in 2 oz. jar or 4" x 2" piece.