Antandrokomby pegmatite, Manandona Valley, Sahatany Pegmatite Field (Mt Bity (Ibity) area), Vakinankaratra Region (Betafo - Antsirabé region), Antananarivo Province, Madagascar

A complex type LCT pegmatite hosted in a metadolomite worked for gem tourmaline, spodumene and beryl from the beginning of the 20th century. Located near the village of Ambatolampy, about 35 kilometers south of Antsirabe, and in the Manandona Valley, south of the Ibity Massif (Mt.Ibity) in the central Highland of Madagascar. Adminstratively the locality is located just outside the border of the Vakinankaratra Region and the Antananarivo Province,and therefore not belongs to these administrative and political units. But since the Antandrokomby pegmatite in all mineralogical litterature is treated as belonging to the Sahatany Pegmatite Field - which most of it are inside the region-border - it is sorted under that hierarchy here in Mindat. (Administratively and politically Antandrokomby is sorted under Ambositra Department, Amoron'iMania Region, Fianaranatsoa Province)
The pegmatite is a steepling dipping dike which measures 350 m x 1,2 meter.

NOTE: Some londonite-rhodizite specimens from the Antsongombato gem mine were sold as coming from here.


Simmons et al (2001) has shown that tourmalines from the Antandrokomby are members of the schorl-elbaite series with significant Mg and Ca content.

References:
- Lacroix, A. (1908): Les minéraux des filons de pegmatite á tourmaline lithique de Madagascar. Bulletin de la Société Francaise de Minéralogie 31: 218- 247

- Lacroix, A. (1912): Sur quelques minéraux des pegmatites du Vakinankaratra (Madagascar). Bulletin de la Société française de Minéralogie, Paris 35 , 76-84 (on danburite and rhodizite)

- Lacroix, A. (1912): Sur une nouvelle espèce minérale (manandonite) des pegmatites de Madagascar. Bulletin de la Société française de Minéralogie, 35, 223-226

- Lacroix, A. (1922): Mineralogie de Madagascar, Tome I. Géologie-Minéralogie descriptive. A.Challamel (Éditeur), Paris. 624p.

- Behier, J. (1963): Carte mineralogique de Madagascar. Archive Service Géologique Madagascar. A 1871

- Ranorosoa, N. , Fontan, F. & Fransolet, A-M. (1989): Rediscovery of manandonite in the Sahatany Valley, Madagascar. European Journal of Mineralogy 1, 633-638

- Ranorosoa, N. (1986): Etude mineralogique des pegmatites du champ de la Sahatany, Madagascar. These de doctorat de L'Universite Paul Sabatier, Toulouse

- Pezzotta F., Falster A.U., Simmons W.B. & Webber K.L. (1997): Rhodizite from Madagascar, new localities and new chemical data. Abstracts of the First International Workshop on Petrology, Milan, Italy, September 11 to 13, 1997, Mus. Storia Nat. Sc. Nat.

- Pezzotta, F. (1999): Madagaskar. Das Paradies der Mineralien und Edelsteine. Extra Lapis nr 17, pp 53-54 (german edition)

- Nizamoff, J.W.; Falster, A.U.; Pezzota, F. ; Simmons, W.B.; Hanson, S.L. and Webber, K.L. (2000): Recent mining at the Antandrokomby pegmatite, Madagascar. 26th Rochester Mineralogical Symposium. Rocks & Minerals, july 2000.

- Nizamoff, J. W.; Falster, A. U.; Pezzota, F.; Simmons, W. B. and Webber, K. L. (2000): Geochemical variation in tourmaline from Antandrokomby, Madagascar. 26th Rochester Mineralogical Symposium. Rocks & Minerals, july 2000.

- Simmons, W. B; Pezzotta, F; Falster, A.U & Webber, K. L. (2001): Londonite, a new mineral species: The Cs-dominant analogue of Rhodizite from the Antandrokomby granitic pegmatite, Madagascar. Canadian Mineralogist 39: 747-755

- Simmons, W.B., Webber, K.L., Falster, A.U., & Nizamoff, J. W. (2001): Gem tourmaline chemistry and paragenesis. Australian gemmologist 21, number 01.

- Pezzotta, F.; Diella, V. & Demartin, F. (2003): Londonit aus Madagaskar- eine neue Mineralart. Lapis 35 (2), 35-38