Marbles for play are often mentioned in Roman literature, and marbles have been found among ancient Egyptian artifacts. Ancient marbles were originally made by hand, usually of clay or stone. Stone marbles were made by grinding and clay marbles were rolled into a ball and then dried, usually by firing in a kiln. Clay marbles could be left natural, painted, or glazed.
Marbles in later times were mostly made from clay, agate or glass, varying in size from about a half inch to one inch in diameter.
Marbles today are made in factories by dropping small globs of molten glass into a groove that rotates as the marble travels along. As the marbles are rotated, they are shaped into spheres. Color can be added to the various batches of marbles being created, or other techniques applied that gives marbles additional interest such as the "cat-eye" marble.
Marbles used to be quite popular in the 1950s and 1960s, and even a little later, but once kids were introduced to video games and other indoor activities, interest declined.