What is tourmaline?
Tourmaline is a supergroup of closely related borosilicate minerals rather than one single mineral species. The canonical group page connects the principal species: Dravite, Elbaite, Schorl, Liddicoatite and Uvite, with Olenite retained as an additional published tourmaline-group species. Species identification depends on chemistry and analysis, not colour alone.
Mineralogy and crystal structure
Tourmalines are trigonal cyclosilicates built from rings of silicon-oxygen tetrahedra and borate groups. Sodium, calcium, lithium, magnesium, iron, aluminium, manganese, chromium, vanadium and fluorine can occupy different structural sites, which explains the wide compositional range. The canonical group structure is a representative tourmaline model; the linked species pages provide more specific chemistry and sources.
Species and trade names
Dravite is commonly sodium-magnesium-rich and brown to black; Elbaite is lithium-rich and supplies much gem material; Schorl is the common iron-rich black species; Liddicoatite is calcium- and lithium-rich; and Uvite is calcium- and magnesium-rich. Rubellite, Indicolite, Verdelite, Achroite, Paraíba and Watermelon Tourmaline are trade or colour names, not a reason to create duplicate species pages. Black Tourmaline is a trade name most often used for Schorl and is linked to that canonical species.
Formation and collecting
Tourmaline forms in granitic pegmatites, hydrothermal veins, schists, marbles and other metamorphic settings. Collectors compare crystals by species, colour zoning, transparency, striations, matrix, locality and treatment history.
Buying and care
For gem material, ask whether the stone is natural, treated and analytically identified. For specimens, preserve the locality label and avoid presenting a colour name as a chemical species. Clean gently with warm water and mild soap, and protect long prisms and terminations from sharp impact.
