The tourmalines are a large group of complex silicates, which can produce crystals in almost every basic hue. As a result, they have become the dominant mid-market gem species and, since the discovery of the neon blue paraiba variety, also now have a significant presence at the high-value end of the market.

While 32 different tourmaline sub-species are recognized by the International Mineralogical Association, the vast majority of gem tourmalines are elbaite. Named after the Italian island of Elba, its various hues have been allocated gemstone tradenames, including rubellite (red/pink), indicolite (greenish-blue/blue), verdelite (green), paraiba (neon blue) and achroite (colorless), as well as a bi-colored, pink and green “watermelon” variety.

Of the remaining 31 tourmaline sub-species, only the black schorl, multi-colored liddicoatite and brownish dravite are of any gemological interest, with chrome-containing specimens of the latter possessing green hues that are amongst the brightest in the gem world.