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Antandrokomby pegmatite, Manandona Valley, Sahatany Pegmatite Field (Mt Ibity area), Vakinankaratra Region, Antananarivo Province, Madagascar
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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. Administratively, the locality is located just outside the border of the Vakinankaratra Region and the Antananarivo Province, and therefore does not belong to these administrative and political units. But since the Antandrokomby pegmatite in all mineralogical literature is treated as belonging to the Sahatany Pegmatite Field - most of which is 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 steeply dipping dike which measures 350 m x 1,2 meter.

NOTES on the mineral list:
- Some londonite-rhodizite specimens from the Antsongombato gem mine were sold as coming from Antandrokomby.

- Nizamoff et al. (2000) and Webber et al (2002) has shown that tourmalines from the miarolitic cavities at the Antandrokomby are members of the elbaite- schorl series with significant Mg and Ca content, and not liddicoatite.

Mineral List

Albite
var: Cleavelandite
Anatase
'Apatite'
Arsenic
Autunite ?
Behierite
Beryl
Bismuth
Brockite
Clinobisvanite
'Clinoptilolite'
Columbite-(Mn)
Danburite
Elbaite
'Elbaite-Schorl Series'
Fluor-liddicoatite
Hambergite
'Heulandite'
Hübnerite
'Liddicoatite' ?
Londonite (TL)
'Londonite-Rhodizite Series'
Manandonite (TL)
Microcline
Microlite Group
var: Cesstibtantite
var: Uranmicrolite (of Hogarth 1977)
Monazite-(Ce)
Opal
Quartz
Rhodizite
Scheelite
Schorl
Spessartine
Spodumene
'Tantalite'
'Tourmaline'
'var: Rubellite'
Xenotime-(Y)


40 entries listed. 28 valid minerals. 2 type localities (valid minerals). 1 erroneous literature entry.

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References

Dabren A. (1906): Sur quelques pierres précieuses de Madagascar. Bulletin de L'Academie malgache. Tananarive, 4:132-137 [First find of spodumen from Antandrokomby]

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

Duparc, L., Wunder, M., Sabot, R. (1910): Les minéraux des pegmatites des environs d´Antsirabe á Madagscar. Mémoires de la Société de Physique et d'Histoire Naturelle de Geneve, 36, 3, 283-407

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

Zheng, H. & Bailey, S.W. (1995): The crystal structure of manandonite-2H2. American Mineralogist. 80: 387-393.

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.

Webber, K. L. Simmons, W. B & Falster, A. U. (2002): Tourmaline from the Antandrokomby and Fianarantsoa Pegmatites, Madagascar. Mineralogical Record 33: 82

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

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