Dating back at least a century, gem-quality blue sapphire has been recovered from alluvial/placer deposits in the Puy-de-Dôme area, located in the Massif Central of France—the largest volcanic region in Europe (M.F. Gonnard, “Sur les gisements gemmifères du Velay et de la basse Auvergne, leur distribution géographique dans ces deux régions, et leurs rapports au point de vue des associations minérales qu'ils renferment,” Bulletin de la Société Française de Minéralogie, Vol. 33, No. 3-4, 1910, pp. 152–161). Recently, several rough sapphires from this location were cut and examined by the authors. The sapphires revealed rich and diverse internal features, including numerous silk-like particles and various mineral inclusions. One specimen hosted a black crystal inclusion with an unusual curved croissant-like shape (see above). Under closer microscopic examination, the black color appeared dark red, viewed most clearly at the two termini.
Raman microspectrometry identified the inclusion as columbite ((Fe,Mn)(Nb,Ta)2O6). Columbite-group minerals belong to the orthorhombic crystal system. While well-formed crystals typically exhibit a prismatic and rectangular shape, crystals that are uneven, thin, acicular, and reddish brown with curved faces have also been documented (A. Siachoque et al., “Occurrence and composition of columbite-(Fe) in the reduced A-type Desemborque Pluton, Graciosa Province (S-SE Brazil),” Minerals, Vol. 10, No. 5, 2020, article no. 411). In addition, columbite inclusions in basaltic sapphires have been reported by Gübelin and Koivula (Photoatlas of Inclusions in Gemstones, Volume 1, ABC Edition, Zurich, 1986, p. 359).
Nevertheless, the unusual curved inclusion makes this French sapphire a uniquely photogenic subject. Although basaltic sapphires are often underestimated, they can be as beautiful as their metamorphic counterparts—a quality that extends to their inclusion scenes as well.
Jonathan Muyal is a global colored stones specialist and brand liaison at GIA in Carlsbad, California. Olena Rybnikova is affiliated with Comenius University in Bratislava, Slovakia. Pierre-Yves Chatagnier is affiliated with Tsara International in Baudemont, France.
Dating back at least a century, gem-quality blue sapphire has been recovered from alluvial/placer deposits in the Puy-de-Dôme area, located in the Massif Central of France—the largest volcanic region in Europe (M.F. Gonnard, “Sur les gisements gemmifères du Velay et de la basse Auvergne, leur distribution géographique dans ces deux régions, et leurs rapports au point de vue des associations minérales qu'ils renferment,” Bulletin de la Société Française de Minéralogie, Vol. 33, No. 3-4, 1910, pp. 152–161). Recently, several rough sapphires from this location were cut and examined by the authors. The sapphires revealed rich and diverse internal features, including numerous silk-like particles and various mineral inclusions. One specimen hosted a black crystal inclusion with an unusual curved croissant-like shape (see above). Under closer microscopic examination, the black color appeared dark red, viewed most clearly at the two termini.
Raman microspectrometry identified the inclusion as columbite ((Fe,Mn)(Nb,Ta)2O6). Columbite-group minerals belong to the orthorhombic crystal system. While well-formed crystals typically exhibit a prismatic and rectangular shape, crystals that are uneven, thin, acicular, and reddish brown with curved faces have also been documented (A. Siachoque et al., “Occurrence and composition of columbite-(Fe) in the reduced A-type Desemborque Pluton, Graciosa Province (S-SE Brazil),” Minerals, Vol. 10, No. 5, 2020, article no. 411). In addition, columbite inclusions in basaltic sapphires have been reported by Gübelin and Koivula (Photoatlas of Inclusions in Gemstones, Volume 1, ABC Edition, Zurich, 1986, p. 359).
Nevertheless, the unusual curved inclusion makes this French sapphire a uniquely photogenic subject. Although basaltic sapphires are often underestimated, they can be as beautiful as their metamorphic counterparts—a quality that extends to their inclusion scenes as well.
Jonathan Muyal is a global colored stones specialist and brand liaison at GIA in Carlsbad, California. Olena Rybnikova is affiliated with Comenius University in Bratislava, Slovakia. Pierre-Yves Chatagnier is affiliated with Tsara International in Baudemont, France.
