Tourmaline: a gemstone name with Singhalese roots

The gemstone name tourmaline is though to derive form a Singhalese (Sinhalese, Cingalese) word or a variant thereof: turmali, tourmali, turamali, thuramali and thoramali are some of its spellings that can be found in the literature, buyer's guides and on websites [1-5]. The name means “mixed parcel,” referring to the large variety of color combinations in which its gemstone specimens occur [3,4]. Originally, the term tourmaline was applied to zircon and other gems by jewelers of Ceylon (now Sri Lanka) [5].

Localities for tourmaline specimens include places in Asia, Europe, Africa, North and South America and even Antarctica (map in [2]). Dutch traders, shipping tourmaline stones from Sri Lanka to Europe, called them Aschentrecker (“ash puller”) due to their pyroelectric properties [1]. Tourmaline is also thought to be identical with lyngurium, described by the ancient Greek scholar Theophrastus of Eresus  (c. 371-285 BC) in his work on stones, De lapidibus,—mistaken as solidified lynx urine.

Classified as a semi-precious stone, tourmaline actually comes in different species and varieties. The Dictionary of Geology and Mineralogy [6] defines tourmaline as “any of a group of cyclosilicate minerals with a complex chemical composition, vitreous to resinous luster, and variable color, crystallizes in the ditrigonal-pyramidal class of the hexagonal system, has piezoelectric properties, and is used as a gemstone.” The dictionary gives the general formala,

(Na,Ca)(Al,Fe,Li,Mg)₃Al₆(BO₃)₃Si₆O₁₈(OH)₄,

which has to be modified to a more specific one when particular species are considered. To better understand the crystal structure of tourmalines, one may, for example, consult the CrystalMaker®-generated drawings by  Darrell Hennry and Barbara Dutrow (page 20 in [1]), depicting structural features of one of the most common tourmaline species, schorl (NaFe²⁺₃,Al₆Si₆O₁₈(BO₃)₃(OH)₃OH). Their figures demonstrate ion and polyhedra arrangement and, in particular, the cyclosilicate-coordinated structure based on rings of six SiO₄ tetraeder (the Si₆O₁₈ unit in the formula). Further, these authors explain the composition and color zoning structure of tourmalines and their significance as forensic objects in earth science and natural history. 

Keywords: geology, mineralogy, gemstones, lapidary, crystal morphology, linguistics, terminology.

References and more to explore
[1] Darrell J. Henry and Barbara L. Dutrow: The Tourmaline Diaries. Natural History March 2012, 120 (3), 16-27.
[2] mindat.org: Tourmaline [www.mindat.org/min-4003.html].
[3] Richard W. Hughes: Palegems.com Tourmaline Buying Guide [www.palagems.com/tourmaline_buyers_guide.htm].
[4] gemselect.com: Tourmaline's name... [www.gemselect.com/gem-info/tourmaline/tourmaline-info.php].
[5] Richard Scott Mitchell: Mineral Names. What do they mean? Van Nostrand Reinhold Company, New York, 1979; page 192.
[6] Dictionary of Geology & Mineralogy. Second Edition. McGraw Hill, New York, 2003.