Final answer:
Tourmaline minerals and gem varieties differ in color due to their chemical compositions and the presence of trace elements. Each variety, such as dravite, indicolite, rubellite, verdelite, paraiba, and watermelon tourmaline, has distinctive colors from different impurities, similar to how rubies and emeralds get their colors from chromium impurities.
Step-by-step explanation:
The tourmaline minerals and gem varieties exhibit differences primarily due to their chemical composition and the trace elements that cause their distinct colors. For instance, dravite is typically a brown or yellow-brown variety that gets its color from magnesium, whereas indicolite is a blue or blue-green variety colored by iron and sometimes a bit of titanium. Rubellite is the pink to red variety of tourmaline, and its vibrant hues often stem from manganese. Moving on to verdelite, this is the green variety that may get its color from iron, chromium, or vanadium in the structure of the mineral.
The highly sought-after paraiba tourmaline is a rare variety that displays neon blues and greens, and the intensity of its color is due to copper and sometimes manganese impurities. Lastly, watermelon tourmaline is named for its unique color zoning that resembles a watermelon with a green rind and pink interior. It is interesting to note that gemstones like ruby and emerald also have their colors induced by trace elements, such as chromium (Cr³+), within the metal oxide lattice of the mineral structure.