Many other substances have been detected in tea from time to time, but not with sufficient frequency to render it necessary to go into a very full account. It is said by some authorities that catechu has been sometimes used to give character and strength to the tea. Besides the soapstone, gypsum, etc., already mentioned, barytes, and other heavy mineral matters have been used for facing to increase weight. Even metallic iron has been found added to teas in some cases to increase weight; also the magnetic oxid of iron, particles of sand, pieces of brick, etc., are sometimes found, but probably accidentally occurring.

It is a mistake to suppose, however, that the green color of tea is due to copper, although this has often been charged. It is doubtful if copper has ever been employed for coloring tea.

Iron salts have been added to tea for the purpose of deepening the color of the infusion.