About Tourmalines
The tourmaline group is, chemically, the most complex of all the major gemstone families — a sub-group of the cyclosilicate minerals with a generalised formula that can accommodate sodium, calcium, lithium, magnesium, iron, manganese, aluminium, and chromium in the same crystal structure, in dozens of possible substitutions. The result is a family of minerals that produces gem-quality crystals in every colour of the visible spectrum, including, uniquely among the major gems, single crystals that display two or three sharply zoned colours simultaneously (the celebrated “watermelon” tourmalines, with a green outer rim and a pink core).
The most commercially important members of the family, in approximate order of value, are: Paraiba tourmaline (copper- and manganese-bearing elbaite tourmaline displaying an extraordinary “neon” blue, green, or violet colour, discovered in the Paraiba state of Brazil in 1989 and subsequently identified in Mozambique and Nigeria); rubellite (the deep-red and hot-pink elbaite tourmalines, principally from Mozambique, Madagascar, and Brazil); indicolite (the deep-blue iron-bearing elbaites); chrome tourmaline (the rich green chromium- and vanadium-bearing dravites of Tanzania); and the multicolour watermelon and parti-coloured tourmalines that have been a connoisseur's favourite for over a century.
Paraiba tourmaline is, on a per-carat basis, among the most valuable coloured stones in the modern trade. Fine Brazilian Paraiba material from the original Heitor Dimas Barbosa mines can command per-carat prices comparable to fine Colombian emerald or Burma ruby, and the Mozambique copper-bearing tourmalines (sometimes marketed as “Paraiba-type,” though now widely accepted as Paraiba tourmaline in the LMHC harmonised nomenclature) have produced fine larger stones that have set successive auction records since 2010. Origin determination on Paraiba — Brazil versus Mozambique versus Nigeria — is one of the most demanding analytical tasks in modern coloured-stone gemmology, requiring LIBS trace-element analysis combined with detailed inclusion study, and AGL's laboratories deploy the full instrumental protocol on every Paraiba submission.
Treatment disclosure is critical in tourmaline grading. Heat treatment is widely applied to improve the blue of indicolite, the red of rubellite, and most especially the colour of copper-bearing Paraiba material, where heating in a controlled atmosphere converts brown and purplish rough into the celebrated “electric blue” or “neon green” colours of the finished stone. Irradiation is occasionally used to deepen colour and is unstable enough to require explicit disclosure. The AGL tourmaline certificate identifies the species and variety within the tourmaline group (elbaite, dravite, schorl, liddicoatite), confirms or excludes copper- or manganese-bearing chemistry (a critical commercial distinction for Paraiba claims), declares the heat-treatment status, and where analytically supportable, determines the country of origin — the four findings that together establish tourmaline value in the contemporary international market.
How AGL certifies Tourmalines
Every tourmalines submitted to an AGL laboratory is examined by at least two senior gemologists and analysed using our standard instrumental package: refractive-index and specific-gravity measurement, microscopic examination under dark-field and fibre-optic illumination, UV-VIS-NIR absorption spectroscopy, FTIR spectroscopy for treatment detection, and LIBS or ED-XRF for trace-element analysis where origin is in question. Every conclusion on the certificate — species, variety, treatment, origin — is supported by recorded analytical data, and every certificate is recorded in our secure verification database for online authentication at any time.
For full service descriptions and turnaround times, see our Services page, or contact your nearest AGL laboratory for a written quotation.
