(Anjanabonoina, Kaominina Ambohimanambola, Departementa Betafo, Faritra Vakinankaratra, Faritany Antananarivo, Madagasikara)
A pegmatite famous for its large and multicolored tourmaline. Located 42 km WSW of the town Betafo in the central highland of Madagascar.
These pegmatite dikes outcrop at an elevation of about 1,400 meters on the eastern slope of Mount Ikaka and are emplaced in a complex environment characterized by paragneiss, marble and orthogneiss of the Neoproterozoic Itremo Group, of medium metamorphic grade. The subhorizontal bodies of pegmatite are strongly zoned. The metasedimentary rocks hosting the pegmatitic dikes locally show extensive contact-metasomatic phenomena. Abundant tourmalization extensively affected schist and quartzite units, with schorl-dravite replacing up to 30% of the rock volume Veins of quartz, dravite-schorl and danburite are locally present in metasedimentary rocks close to the pegmatites, and marble is transformed into skarn (De Vito et al 2006).
References:
Lacroix, A. (1909): Sur la hambergite de Madagascar. Bulletin de la Société francaise de Minéralogie, Paris. 32, 320-324
Lacroix, A.(1922-23): Minéralogie de Madagascar. Tome I-III, Paris.
Bancroft, P.: Gem & Crystal Treasures, 322-325.
Strunz, H. (1979) Anjanabonoina, Fundort schönnnnnnnnster Tourmaline. Lapis: 4: 24-27, 47-48.
Wilson, W.E. (1989) The Anjanabonoina pegmatite, Madagascar. Mineralogical Record (1989): 20: 191-200.
Extra Lapis 17. Madagascar, 56-59 (in German).
De Vito, C., Aurisicchio, C., Ferrini, V., and Pezzotta, F. (2002a) Nb-Ta oxides from Anjanabonoina pegmatite. International Mineral. Assoc. 18th General Meeting (Edinburgh), Program Abstract: 275.
De Vito, C., Aurisicchio, C., Ferrini, V., and Pezzotta, F. (2002b) Chemical composition and B, O and H isotopes of tourmaline from Anjanabonoina pegmatite. International Mineral. Association, 18th General Meeting (Ednburgh), Program Abstract: 208.
Dini, A., Tonarini, S., Pezzotta, F., and De Vito, C. (2002) Boron isotopes study of borates and boro-silicates from Anjanabonoina and Tetezantsio pegmatites (central Madagascar). International Mineral. Association, 18th General Meeting (Edinburgh), Program Abstract: 210.
Dirlam, D.M., Laurs, B.M., Pezzotta, F., and Simmons, W.B. (2002) Liddicoatite tourmaline from Anjanabonoina, Madagascar. Gems and Gemology: 38: 28-52.
De Vito, C., Pezzotta, F., Ferrini, V., and Aurisicchio, C. (2006) Nb-Ti-Ta oxides in the gem-mineralized and "hybrid" Anjanabonoina granitic pegmatite, central Madagascar: A record of magmatic and postmagmatic events. Canadian Mineralogist: 44: 87-103.
