What is a common metal found in many Paraiba tourmalines?

Paraiba tourmalines are notable for their vibrant, neon blue and green colors, which primarily result from the presence of copper in their chemical composition. Copper is a key trace element that imparts the distinctive coloration to these gemstones. It's this unique aspect that sets Paraiba tourmalines apart from other types of tourmalines, which typically owe their colors to different metal ions, such as iron or manganese.

In addition, while other metals like aluminum, iron, and magnesium can be present in various types of tourmalines, they do not contribute to the extraordinary hues for which Paraiba tourmalines are known. Copper's role in the formation of these stones is crucial, as it alters the absorption spectrum of the crystal, allowing it to reflect the vivid colors that gemstone enthusiasts appreciate.

Thus, the answer focuses on the pivotal role copper plays in the aesthetic and chemical identity of Paraiba tourmalines, making it the correct choice in this context.