The term 'Glass Marble' can be broken down into two crossword solutions: AGATE (5 letters) and IMMIE (5 letters). AGATE is a type of quartz that is often used to make jewelry and other decorative items. It is usually found in a variety of colors, including white, gray, pink, and brown. Immie is a type of glass marble that is made from a combination of glass and metal. It is usually found in bright colors, such as red, blue, and yellow. Both AGATE and immie are popular materials for making glass marbles.