Cap Andrahomana, Andranobory, Taolagnaro District, Anosy, Madagascari
| Regional Level Types | |
|---|---|
| Cap Andrahomana | Outcrop |
| Andranobory | Commune |
| Taolagnaro District | District |
| Anosy | Region |
| Madagascar | Country |
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Latitude & Longitude (WGS84):
25° 11' 57'' South , 46° 37' 56'' East
Latitude & Longitude (decimal):
Type:
Köppen climate type:
Other Languages:
Malagasy:
Cap Andrahomana, Kaominin' Andranobory, Distrikan'i Taolañaro, Faritr' Anosy, Madagasikara
Cap Andrahomana is situated WSW of the town Fort Dauphin (Taolanaro), at the southernmost point of the mountain range Chaînes Anosyennes. Here a small granitic pegmatite was exposed in a 40 m high coastal cliff close to the seashore. The pegmatite cross-cuts migmatitic high-grade granulite-facies (800 °C, 5-5.5 kb, 561 +/- 12 Ma) metapelite gneisses and leptynites.
The pegmatite is the type locality of grandidierite, where it was found in 1902 as up to 8 cm long crystals.
The locality was first discovered by Charles Allaud (1861-1949), a French biologist and explorer, during his expedition to the southern part of Madagascar 1900-1901. Specimens collected during this expedition were sent to the French mineralogist Alfred Lacroix in Paris. Among the samples, Lacroix found a fragment of a greenish blue unknown mineral. A preliminary note on this new mineral, given the name grandidierite was published in 1902.
Additional samples were collected by the French commandant Blondlat at Fort Dauphin and sent to Lacroix.
Later, in the 1920s, Raymond Decary, a French colonial administrator, ethnologist, and explorer investigated the area, did some blasting at the grandidierite-bearing pegmatite, and found some samples. However, according to Béhier (1960), when his co-worker C. Mignot was able to locate the site in 1960 he could not find any more traces of grandidierite here (Larsen 2023).
NOTE:
Samples of grandidierite found in other localities further north (Vohibola, Marotrana, Sahakondro and other localities) have often erroneously been labelled as coming from Andrahomana. For many years, Andrahomana was the only locality cited in textbooks on mineralogy.
Select Mineral List Type
Standard Detailed Gallery Strunz Chemical ElementsMineral List
12 valid minerals. 1 (TL) - type locality of valid minerals.
Rock Types Recorded
Note: data is currently VERY limited. Please bear with us while we work towards adding this information!
Select Rock List Type
Alphabetical List Tree DiagramDetailed Mineral List:
| ⓘ Almandine Formula: Fe2+3Al2(SiO4)3 |
| ⓘ Andalusite Formula: Al2(SiO4)O Habit: microscopic crystals Colour: Rose-coloured in center and colourless at the rims of the crystals Description: Late phase. |
| ⓘ 'Apatite' Formula: Ca5(PO4)3(Cl/F/OH) |
| ⓘ 'Biotite' Formula: K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 Description: Late phase. |
| ⓘ Cordierite Formula: (Mg,Fe)2Al3(AlSi5O18) Description: Rims hercynite at the contact of quartz and feldspars. References: |
| ⓘ Enstatite Formula: Mg2Si2O6 References: |
| ⓘ 'Garnet Group' Formula: X3Z2(SiO4)3 |
| ⓘ Grandidierite (TL) Formula: (Mg,Fe2+)(Al,Fe3+)3(SiO4)(BO3)O2 Type Locality: Habit: masses up to several centimeters across Colour: Bluish green Description: C. Mignot was not able to find any more grandidierite at the site in 1960 (Behier 1960) |
| ⓘ Hercynite Formula: Fe2+Al2O4 Description: Green hercynite+quartz assemblages (high-grade metamorphism).
Hercynite : 0.6% ZnO, 0.4% Cr2O3. References: |
| ⓘ Ilmenite Formula: Fe2+TiO3 Description: Niobian ilmenite. |
| ⓘ 'K Feldspar' Colour: gray Description: perthitic |
| ⓘ Microcline Formula: K(AlSi3O8) |
| ⓘ 'Monazite Group' Formula: REE(PO4) References: |
| ⓘ Quartz Formula: SiO2 |
| ⓘ Sillimanite Formula: Al2(SiO4)O |
| ⓘ Spinel Formula: MgAl2O4 References: |
| ⓘ 'UM1998-//-BOSiO:AlFeMg[2]' Formula: (Fe2+,Mg)2Al14Si4B4O37 |
| ⓘ Werdingite Formula: (Mg,Fe)2Al14Si4B4O37 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. |
Gallery:
List of minerals arranged by Strunz 10th Edition classification
| Group 4 - Oxides and Hydroxides | |||
|---|---|---|---|
| ⓘ | Hercynite | 4.BB.05 | Fe2+Al2O4 |
| ⓘ | Spinel | 4.BB.05 | MgAl2O4 |
| ⓘ | Ilmenite | 4.CB.05 | Fe2+TiO3 |
| ⓘ | Quartz | 4.DA.05 | SiO2 |
| Group 9 - Silicates | |||
| ⓘ | Almandine | 9.AD.25 | Fe2+3Al2(SiO4)3 |
| ⓘ | Sillimanite | 9.AF.05 | Al2(SiO4)O |
| ⓘ | Andalusite | 9.AF.10 | Al2(SiO4)O |
| ⓘ | Grandidierite (TL) | 9.AJ.05 | (Mg,Fe2+)(Al,Fe3+)3(SiO4)(BO3)O2 |
| ⓘ | Werdingite | 9.BD.35 | (Mg,Fe)2Al14Si4B4O37 |
| ⓘ | Cordierite | 9.CJ.10 | (Mg,Fe)2Al3(AlSi5O18) |
| ⓘ | Enstatite | 9.DA.05 | Mg2Si2O6 |
| ⓘ | Microcline | 9.FA.30 | K(AlSi3O8) |
| Unclassified | |||
| ⓘ | 'Biotite' | - | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| ⓘ | 'Monazite Group' | - | REE(PO4) |
| ⓘ | 'UM1998-//-BOSiO:AlFeMg[2]' | - | (Fe2+,Mg)2Al14Si4B4O37 |
| ⓘ | 'K Feldspar' | - | |
| ⓘ | 'Garnet Group' | - | X3Z2(SiO4)3 |
| ⓘ | 'Apatite' | - | Ca5(PO4)3(Cl/F/OH) |
List of minerals for each chemical element
| H | Hydrogen | |
|---|---|---|
| H | ⓘ Biotite | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| H | ⓘ Apatite | Ca5(PO4)3(Cl/F/OH) |
| B | Boron | |
| B | ⓘ Grandidierite | (Mg,Fe2+)(Al,Fe3+)3(SiO4)(BO3)O2 |
| B | ⓘ Werdingite | (Mg,Fe)2Al14Si4B4O37 |
| B | ⓘ UM1998-//-BOSiO:AlFeMg[2] | (Fe2+,Mg)2Al14Si4B4O37 |
| O | Oxygen | |
| O | ⓘ Andalusite | Al2(SiO4)O |
| O | ⓘ Almandine | Fe32+Al2(SiO4)3 |
| O | ⓘ Biotite | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| O | ⓘ Cordierite | (Mg,Fe)2Al3(AlSi5O18) |
| O | ⓘ Enstatite | Mg2Si2O6 |
| O | ⓘ Grandidierite | (Mg,Fe2+)(Al,Fe3+)3(SiO4)(BO3)O2 |
| O | ⓘ Hercynite | Fe2+Al2O4 |
| O | ⓘ Ilmenite | Fe2+TiO3 |
| O | ⓘ Microcline | K(AlSi3O8) |
| O | ⓘ Monazite Group | REE(PO4) |
| O | ⓘ Quartz | SiO2 |
| O | ⓘ Sillimanite | Al2(SiO4)O |
| O | ⓘ Spinel | MgAl2O4 |
| O | ⓘ Werdingite | (Mg,Fe)2Al14Si4B4O37 |
| O | ⓘ UM1998-//-BOSiO:AlFeMg[2] | (Fe2+,Mg)2Al14Si4B4O37 |
| O | ⓘ Garnet Group | X3Z2(SiO4)3 |
| O | ⓘ Apatite | Ca5(PO4)3(Cl/F/OH) |
| F | Fluorine | |
| F | ⓘ Biotite | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| F | ⓘ Apatite | Ca5(PO4)3(Cl/F/OH) |
| Mg | Magnesium | |
| Mg | ⓘ Biotite | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| Mg | ⓘ Cordierite | (Mg,Fe)2Al3(AlSi5O18) |
| Mg | ⓘ Enstatite | Mg2Si2O6 |
| Mg | ⓘ Grandidierite | (Mg,Fe2+)(Al,Fe3+)3(SiO4)(BO3)O2 |
| Mg | ⓘ Spinel | MgAl2O4 |
| Mg | ⓘ Werdingite | (Mg,Fe)2Al14Si4B4O37 |
| Mg | ⓘ UM1998-//-BOSiO:AlFeMg[2] | (Fe2+,Mg)2Al14Si4B4O37 |
| Al | Aluminium | |
| Al | ⓘ Andalusite | Al2(SiO4)O |
| Al | ⓘ Almandine | Fe32+Al2(SiO4)3 |
| Al | ⓘ Biotite | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| Al | ⓘ Cordierite | (Mg,Fe)2Al3(AlSi5O18) |
| Al | ⓘ Grandidierite | (Mg,Fe2+)(Al,Fe3+)3(SiO4)(BO3)O2 |
| Al | ⓘ Hercynite | Fe2+Al2O4 |
| Al | ⓘ Microcline | K(AlSi3O8) |
| Al | ⓘ Sillimanite | Al2(SiO4)O |
| Al | ⓘ Spinel | MgAl2O4 |
| Al | ⓘ Werdingite | (Mg,Fe)2Al14Si4B4O37 |
| Al | ⓘ UM1998-//-BOSiO:AlFeMg[2] | (Fe2+,Mg)2Al14Si4B4O37 |
| Si | Silicon | |
| Si | ⓘ Andalusite | Al2(SiO4)O |
| Si | ⓘ Almandine | Fe32+Al2(SiO4)3 |
| Si | ⓘ Biotite | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| Si | ⓘ Cordierite | (Mg,Fe)2Al3(AlSi5O18) |
| Si | ⓘ Enstatite | Mg2Si2O6 |
| Si | ⓘ Grandidierite | (Mg,Fe2+)(Al,Fe3+)3(SiO4)(BO3)O2 |
| Si | ⓘ Microcline | K(AlSi3O8) |
| Si | ⓘ Quartz | SiO2 |
| Si | ⓘ Sillimanite | Al2(SiO4)O |
| Si | ⓘ Werdingite | (Mg,Fe)2Al14Si4B4O37 |
| Si | ⓘ UM1998-//-BOSiO:AlFeMg[2] | (Fe2+,Mg)2Al14Si4B4O37 |
| Si | ⓘ Garnet Group | X3Z2(SiO4)3 |
| P | Phosphorus | |
| P | ⓘ Monazite Group | REE(PO4) |
| P | ⓘ Apatite | Ca5(PO4)3(Cl/F/OH) |
| Cl | Chlorine | |
| Cl | ⓘ Apatite | Ca5(PO4)3(Cl/F/OH) |
| K | Potassium | |
| K | ⓘ Biotite | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| K | ⓘ Microcline | K(AlSi3O8) |
| Ca | Calcium | |
| Ca | ⓘ Apatite | Ca5(PO4)3(Cl/F/OH) |
| Ti | Titanium | |
| Ti | ⓘ Biotite | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| Ti | ⓘ Ilmenite | Fe2+TiO3 |
| Fe | Iron | |
| Fe | ⓘ Almandine | Fe32+Al2(SiO4)3 |
| Fe | ⓘ Biotite | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| Fe | ⓘ Cordierite | (Mg,Fe)2Al3(AlSi5O18) |
| Fe | ⓘ Grandidierite | (Mg,Fe2+)(Al,Fe3+)3(SiO4)(BO3)O2 |
| Fe | ⓘ Hercynite | Fe2+Al2O4 |
| Fe | ⓘ Ilmenite | Fe2+TiO3 |
| Fe | ⓘ Werdingite | (Mg,Fe)2Al14Si4B4O37 |
| Fe | ⓘ UM1998-//-BOSiO:AlFeMg[2] | (Fe2+,Mg)2Al14Si4B4O37 |
Other Regions, Features and Areas containing this locality
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References
Lacroix, Alfred (1902) Note préliminaire sur une nouvelle espèce minérale. Bulletin de la Société française de Minéralogie, 25 (4-5) 85-86
Lacroix, Alfred (1922) Minéralogie de Madagascar, Tome I. Géologie-Minéralogie descriptive. Augustin Challamel. 624 pp.
Decary, Raymond (1927) Les Gneiss à Grandidierite d'Andrahomana (Madagascar) Bulletin du Muséum national d'histoire naturelle, S. 1 Vol. 33. Muséum national d'histoire naturelle. 556-557
Behier, Jean (1960) Travaux minéralogiques. Rapport Annuel du Service géologique, 1960. Republique Madagascar. 181-199p.194 - note on a search for grandidierite in 1960
Cap Andrahomana, Andranobory, Taolagnaro District, Anosy, Madagascar