Tourmaline is known for its extensive array of colours, making it widely regarded as the gemstone with the broadest colour range. In many cases, deeply coloured tourmalines also exhibit a remarkable phenomenon called pleochroism. For instance, red tourmaline may display shades of deep red and pink, while green tourmaline can showcase various shades within the green spectrum. This pleochroism adds to the captivating and diverse nature of tourmaline gemstones.
Tourmaline crystals often exhibit spectacular formations, with some displaying multi-coloured characteristics. These crystals can feature different colours at each end or form colour-zoned cores and rims. Lapidaries sometimes take advantage of these unique properties when cutting tourmaline, resulting in bi-coloured gemstones known as "parti-coloured" and "watermelon" tourmaline.
Tourmaline is a group name encompassing several species distinguished by their varied chemical compositions. Specific colour variations within the group are known by special names, such as "rubellite" for red tourmaline and "schorl" for black tourmaline. Among the various colour varieties, the bright electric blue to green Paraiba tourmaline stands out as one of the most highly coveted and sought-after gemstones.
Upon undergoing heat treatment and meticulous faceting, these gemstones radiate an astonishing "neon" glow, making them truly extraordinary. As a result of this exceptional quality, they are associated with remarkably high prices in the market.
Tourmaline predominantly forms in rocks like granites and related coarse-grained rocks known as pegmatites. Crystals are often found within pockets in these rocks, accounting for a significant portion of the world's supply of gem-quality material.
Due to the intricate factors influencing the coloration of tourmaline, the outcomes of different treatments can be unpredictable and variable. Heat treatment and irradiation are commonly employed techniques to enhance the gem's color, while waxing or oiling may be used to conceal fractures or fill cracks. It's worth noting that synthetic tourmaline has not been successfully created, limiting imitations to other natural stones or artificial materials like glass.