Many tourmalines owe their color to a mixture of metal ions.
The great diversity of color in tourmalines is due the the variability in which these mixtures occur. Images of Tourmaline Slices For images of colorful tourmaline slices and more information about their color go to the section on tourmaline slices . Black in mass, blue when very thin. The black crystal that most people would call schorl is green when thin. Black crystal, blue when thin.