Tourmaline the Indicator Mineral: From Atomic Arrangement to Viking Navigation

Tourmaline sensulato has been known for at least two thousand years, and its unique combination of physical properties has ensured its importance to human society, from technical devices (such as a possible Viking navigational aid and early piezoelectric gauges in the 20th century) to attractive and popular gemstones. The chemical diversity and accommodating nature of its structure combine to make tourmaline a petrogenetic indicator for the wide range of rocks in which it occurs. Recent advances in understanding the structure, site assignments, and substitution mechanisms have led to a new nomenclature for the tourmaline supergroup minerals. Eighteen species have been described to encapsulate the chemical variety found in this intriguing structure.