Modern marbles are made from a combination of sand, soda lime, silica, and several other ingredients added for pigment or decoration. These other additives range from aluminum hydrate to zinc oxide. The primary component, sand, is essentially loose, granular particles of disintegrated rock. Soda lime is the chemical term for the mixture of calcium hydroxide and sodium or potassium hydroxide. It is a drying agent and absorbs carbon dioxide. Another compound used in marble manufacturing is silica, a white or colorless crystalline found in agate, flint, quartz, and other rocks. Some marbles are also made from cullet, or scrap glass.