Why do we call these orbs "marbles"? It seems strange to call small spheres made of glass, clay, or semiprecious stones "marbles." The best-known marbles actually made of marble consist limestone from Germany, and very few marbles (as in the toy) were actually made of marble (as in the stone). Most of the marbles that kids use to play games are actually made of glass. American and German toy makers devised glass-marble machines in the first decade of the 20th century, and marbles have remained popular toys every since.