In August 2001, the Gübelin Gem Lab (GGL) received samples of tourmaline from firms in Idar-Oberstein, Germany (Gebrüder Bank, Wild & Petsch, and Paul Wild) that also reportedly were from a new deposit near Ilorin, Nigeria. We were informed by these suppliers that the tourmalines from this deposit are found in a wide range of colors, many of which are similar to those observed in “Paraíba” tourmalines from the São José da Batalha mine in Brazil. According to the suppliers, most of the Nigerian material—like the Brazilian tourmalines—is heat treated; after heat treatment, the majority of the tourmaline is sold in Germany and in Brazil.

The Nigerian tourmalines studied at GGL were submitted by the dealers before heat treatment, and consisted of a 22.98 ct violet gemstone (see figure, photo by Franzisca Imfeld), six purplish pink to blue crystal pieces (0.69–1.44 ct), and a 3.30 ct bluish green piece. Standard gemological properties obtained for the 22.98 ct stone were typical for gem tourmaline: R.I.—n_ω=1.620, n_ε=1.638; birefringence—0.018; optic character—uniaxial negative; and inert to short- and long-wave UV radiation. Internal features consisted of the typical liquid inclusions observed in tourmalines, some of which contained a secondary gas bubble. The gemstone displayed moderately strong pleochroism consisting of purple-violet parallel to the optic axis and slightly grayish violet-blue perpendicular to the optic axis. A distinct color change was visible when the stone was viewed in day- or fluorescent light (violet) and incandescent light (purple).

EDXRF qualitative chemical analysis of the violet gemstone and the purplish pink to blue pieces revealed the presence of copper, as well as manganese, iron, and bismuth, in varying relative intensities. The bluish green slice contained relatively high concentrations of iron and manganese, but no copper was detected.

Copper-manganese-bearing elbaite from Nigeria was recently documented by J. W. Zang et al. (“Cu-haltige Elbaite aus Nigeria,” Berichte der Deutschen Mineralogischen Gesellschaft, Beihefte zum European Journal of Mineralogy, Vol. 13, 2001, p. 202), who reported the source as the Edeko area, near Ilorin in western Nigeria. These authors obtained quantitative chemical analyses of three violet-blue samples (J. Zang, pers. comm., 2001) that are consistent with the results we obtained; using an electron microprobe and laser mass spectrometry, they measured 2.13–2.59 wt.% MnO, 0.51–2.18 wt.% CuO, 0–0.05 wt.% TiO₂, 0–0.02 wt.% FeO, and 0–0.02 wt.% Bi₂O₃, as well as other minor and trace elements. Prior to this new find, cuprian elbaite was known only from the Paraíba and Rio Grande do Norte states in northeast Brazil (see, e.g., E. Fritsch et al., “Gem-quality cuprian-elbaite tourmalines from São José da Batalha, Paraíba, Brazil,” Fall 1990 Gems & Gemology, pp. 189–205; J. Karfunkel and R. R. Wegner, “Paraiba tourmalines—Distribution, mode of occurrence, and geologic environment,” Canadian Gemmologist, Vol. 17, No. 4, 1996, pp. 99–106).

Tourmaline mining in the Edeko area is reportedly unorganized, with up to several thousand miners working the area. At this time, the amount of copper-manganese-bearing tourmaline produced from there is not known. Some reports indicate that over 100 kg of Edeko rough have been sent to Idar-Oberstein, but very little of the material is of high quality, and even less has enough copper to attain the intense “Paraíba”-like blue, blue-green, and “turquoise” colors (J. W. Zang, pers. comm., 2001).