Material

• Clay marbles were made of several different types of clay, with different densities and glazes. Because they were often made of local clay and imperfectly made, they were not highly valued when they were being produced.
  
  

Eye Appeal

• Eye appeal is one of the factors that determines the value of marbles. Clay marbles do not usually have the eye appeal of glass, agate or porcelain marbles, so are valued less.
  
  

Rarity

• Marbles that are more rare and difficult to find are valued higher than more common marbles. Because clay marbles were produced so prolifically they were referred to as "commons" or "commies." These clay marbles are still relatively common, which reduces their value.
  
  

Condition

• Marble condition, the number of chips or cracks in it, affects the value of it. Clay marbles were often glazed or painted, which makes the clay marbles more susceptible to damage than other marbles.
  
  

Size

• The larger a marble is, the more it is worth, no matter what material it is made of.