Glass with a distinctive bright metallic look created by adding small particles of copper to the molten glass. The word avventurina originated to describe the difficulty of its production, considered to be a ventura, an adventure in Venetian dialect. It is produced by gradually adding to the cristallo glass mixture the required quantities of reducing substances. After a very slow cooling process the reduced glass mixture will produce small copper crystals. The copper crystals, when separated from the melted mixture, will give the glass an unusual copper finish.