What is a common metal found in many Paraiba tourmalines?

The correct answer is copper. Paraiba tourmaline is a gemstone that is renowned for its vibrant blue to green colors, which are primarily due to the presence of copper in its chemical composition. This trace element, along with manganese, contributes to the unique hues that set Paraiba tourmaline apart from other types of tourmaline. The distinctive coloration resulting from copper is what makes these stones highly sought after and valuable.

While aluminum, iron, and magnesium are also elements found in various types of tourmaline, they are not responsible for the characteristic colors of Paraiba tourmaline. Instead, these elements are more commonly associated with other varieties of tourmaline or different mineral structures. For instance, aluminum is a part of tourmaline's general formula, but it does not play a significant role in defining the color of Paraiba stones. Iron and magnesium can influence certain colors and properties in other types of tourmaline but are not linked to the distinctive coloring of Paraiba tourmaline.