Marble (toy) conventions. Additionally, many glass artisans produce art marbles for the collectors' market only, with some selling for thousands of dollars. Marbles are made using many techniques. They can be categorized into two general types: hand-made and machine-made. Marbles were originally made by hand. Stone or ivory marbles can be fashioned by grinding. Clay, pottery, ceramic, or porcelain marbles can be made by rolling the material into a ball, and then letting dry, or firing, and then can be left natural, painted, or glazed. Clay marbles, also known as "crock marbles" or "commies" ("common"), are made of slightly porous clay, traditionally
Elgin Marbles the missing elements clearly marked and space left should they be returned to Athens. Outside Greece a campaign for the Return of the Marbles began in 1981 with the formation of the "International Organising Committee - Australia - for the Restitution of the Parthenon Marbles, and in 1983 with the formation of the ""British Committee for the Reunification of the Parthenon Marbles". International organisations such as UNESCO and the International Association for the Reunification of the Parthenon Sculptures, as well as campaign groups such as, Marbles Reunited, and stars of Hollywood, such as George Clooney and Matt Damon, as well