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Cap Andrahomana, Ranopiso District, Anosy (Fort Dauphin) Region, Tuléar (Toliara) Province, Madagascar

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(Cap Andrahomana, Distrikan'i Ranopiso, Faritra Anosy, Faritany Toliary, Madagasikara)

Cap Andrahomana is situated WSW of the town Fort Dauphin (Taolanaro), at the southernmost point of the mountainrange Chaînes Anosyennes. This is the type locality of grandidierite, where it was found in 1902 in a small pegmatite as up to 8 cm long crystals.
According to Behier (1960) C. Mignot who searched for the site, and found it (in 1960), could not find any more grandidierite at the site.
The pegmatite cross-cuts migmatitic high-grade granulite-facies (800 °C, 5-5.5 kb, 561 +/-12 Ma)metapelite gneisses and leptynites.



References:
- Lacroix, A. (1902): Note préliminaire sur une nouvelle espèce minerale. Bulletin de la Société Francaise de Minéralogie 25: 85-86

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

Behier, J. (1960): Travaux mineralogiques. in Besaire,H. (ed): Rapport Annuel du Service Geologique pour 1960. Republique Malgache, 181-199 [p. 194, note on a search for grandidierite in 1960]

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

- Eur. J. Minéral; , 1991, 3, pp.367-386

- Grew, E. S.; Yates, M. G. ; Huijsmans, J. P. P. ; McGee, J. J.; Shearer, C. K.; Wiedenbeck, M. & Rouse, R. C. (1998): Werdingite, a borosilicate new to granitic pegmatites, The Canadian Mineralogist 36, 399-414





Mineral List:
  		•  Almandine
    Fe
    2+
    3
    		Al
     
    2
    		[SiO
     
    4
    		]
     
    3
    Reference: [Lacroix, A. (1922): Mineralogie de Madagascar, Tome I. Géologie-Minéralogie descriptive. A.Challamel (Éditeur), Paris. p 394]
  		•  Andalusite
    Al
     
    2
    		[O|SiO
     
    4
    		]
    Habit: microscopic crystals
    Colour: Rose-coloured in center and colourless at the rims of the crystals
    Description: Late phase.
    Reference: [Lacroix, A. (1922): Mineralogie de Madagascar, Tome I. Géologie-Minéralogie descriptive. A.Challamel (Éditeur), Paris. pp 403- 404]
  		•  'Apatite'
    Reference: [Behier, J. (1963): Carte mineralogique de Madagascar. Archive Service Géologique Madagascar. A 1871]
  		•  Biotite
    Description: Late phase.
    Reference: [Lacroix, A. (1922): Mineralogie de Madagascar, Tome I. Géologie-Minéralogie descriptive. A.Challamel (Éditeur), Paris. p 394]
  		•  Cordierite
    (Mg,Fe)
     
    2
    		Al
     
    4
    		Si
     
    5
    		O
     
    18
    Description: Rims hercynite at the contact of quartz and feldspars.
    Reference: [Eur. J. Minéral; , 1991, 3, pp.367-386]
  		•  Enstatite
    Mg
     
    2
    		[SiO
     
    3
    		]
     
    2
    Reference: [Eur. J. Minéral; , 1991, 3, pp.367-386]
  		•  'Garnet Group'
    X
     
    3
    		Z
     
    2
    		(TO
     
    4
    		)
     
    3
    		 (X = Ca, Fe, etc·, Z = Al, Cr, etc·, T = Si, As, V)
    Reference: [Behier, J. (1963): Carte mineralogique de Madagascar. Archive Service Géologique Madagascar. A 1871]
  		•  Grandidierite (TL)
    (Mg,Fe
    2+
     
    		)(Al,Fe
    3+
     
    		)
     
    3
    		[O
     
    2
    		|BO
     
    3
    		|SiO
     
    4
    		]
    Type Locality: Cap Andrahomana, Ranopiso District, Anosy (Fort Dauphin) Region, Tuléar (Toliara) Province, Madagascar
    Description: C. Mignot was not able to find any more grandidierite at the site in 1960 (Behier 1960)
    Reference: [Lacroix, A. (1902): Note préliminaire sur une nouvelle espèce minerale. Bulletin de la Société Francaise de Minéralogie 25: 85-86 ; ]
    Site Photo
    Cap Andrahomana, Ranopiso District, Anosy (Fort Dauphin) Region, Tuléar (Toliara) Province, Madagascar
    © Arliguie M
  		•  Hercynite
    FeAl
     
    2
    		O
     
    4
    Description: Green hercynite+quartz assemblages (high-grade metamorphism). Hercynite : 0.6% ZnO, 0.4% Cr2O3.
    Reference: [Eur. J. Minéral; , 1991, 3, pp.367-386]
  		•  Ilmenite
    Fe
    2+
     
    		TiO
     
    3
    Description: Niobian ilmenite.
    Reference: [http://www.mineralogicalassociation.ca/doc/abstracts/cm2_Vol36_Avr98.pdf. / p. 30]
  		•  'K Feldspar'
    Colour: gray
    Description: perthitic
    Reference: [Grew, E. S. et al. (1998): Werdingite, a borosilicate new to granitic pegmatites, The Canadian Mineralogist 36, 399-414 + http://www.mineralogicalassociation.ca/doc/abstracts/cm2_Vol36_Avr98.pdf. / p. 30]
  		•  Microcline
    K[AlSi
     
    3
    		O
     
    8
    		]
    Reference: [Lacroix, A. (1922): Mineralogie de Madagascar, Tome I. Géologie-Minéralogie descriptive. A.Challamel (Éditeur), Paris. p 394]
  		•  'Monazite'
    Reference: [Eur. J. Minéral; , 1991, 3, pp.367-386]
  		•  Quartz
    SiO
     
    2
    Reference: [Lacroix, A. (1922): Mineralogie de Madagascar, Tome I. Géologie-Minéralogie descriptive. A.Challamel (Éditeur), Paris. p 394]
  		•  Sillimanite
    Al
     
    2
    		[O|SiO
     
    4
    		]
    Reference: [Behier, J. (1963): Carte mineralogique de Madagascar. Archive Service Géologique Madagascar. A 1871]
  		•  Spinel
    MgAl
     
    2
    		O
     
    4
    Reference: [Lacroix, A. (1922): Mineralogie de Madagascar, Tome I. Géologie-Minéralogie descriptive. A.Challamel (Éditeur), Paris. p 323 + 394]
  		•  'Unnamed (Fe analogue of Werdingite)'
    (Fe
    2+
     
    		,Mg)
     
    2
    		Al
     
    14
    		Si
     
    4
    		B
     
    4
    		O
     
    37
    Reference: [Grew, E. S. et al. (1998): Werdingite, a borosilicate new to granitic pegmatites, The Canadian Mineralogist 36, 399-414: AmMin 84:993 ]
  		•  Werdingite
    (Mg,Fe)
     
    2
    		Al
     
    14
    		Si
     
    4
    		B
     
    4
    		O
     
    37
    Colour: Shows yellow pleochroism
    Description: Be-werdingite, replaces sillimanite. Found as inclusions in grandidierite or garnet, or as grains 0,05-5mm long and 0,1-2 mm across or as 0,1-2 mm graisn replacing sillimanite.
    Reference: [Grew, E. S. et al. (1998): Werdingite, a borosilicate new to granitic pegmatites, The Canadian Mineralogist 36, 399-414 + [AmMin 84:993]


    18 entries listed. 12 valid minerals. 1 type locality (valid mineral).

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