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Ilakaka gem deposit, Ilakaka Commune, Ihosy District, Ihorombe, Madagascari
Regional Level Types
Ilakaka gem depositDeposit
Ilakaka CommuneCommune
Ihosy DistrictDistrict
IhorombeRegion
MadagascarCountry

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Name(s) in local language(s):Fitrandrahana safiran' Ilakaka, Kaominin' Ilakaka, Distrikan' Ihosy, Faritra Ihorombe, Faritanin'i Fianarantsoa, Madagasikara
Latitude & Longitude (WGS84): 22° 42' 12'' South , 45° 13' 12'' East
Latitude & Longitude (decimal): -22.70336,45.22001
GeoHash:G#: m5bnv4bpq
Locality type:Deposit
Köppen climate type:Cfa : Humid subtropical climate
Nearest Settlements:
PlacePopulationDistance
Ranohira6,000 (2018)30.6km


An alluvial gem gravel deposit discovered 1998. One of the largest sapphire deposits in the world. It is located Close to the route national 7 going to Tulear, in the Horombe region in the southwestern part of Madagascar.
A large number of new gem deposits of the same character has also been discovered in the area around Ilakaka and further southwest in the Sakaraha area. There is also a third district near Bezaha close to the Onillahy River 118 km southwest of Ilakaka.

NOTE: the name "Ilakaka" in the litterature refers not only to the Ilakaka deposit, but also sometimes to the whole gem deposit area.

Regions containing this locality

Somali Plate (Somalia Plate)Tectonic Plate
Fianarantsoa Province, MadagascarProvince

Select Mineral List Type

Standard Detailed Strunz Dana Chemical Elements

Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.


Mineral List


10 valid minerals.

Detailed Mineral List:

'Almandine-Pyrope Series'
Andalusite
Formula: Al2(SiO4)O
Beryl
Formula: Be3Al2(Si6O18)
Chrysoberyl
Formula: BeAl2O4
Chrysoberyl var: Alexandrite
Formula: BeAl2O4
Corundum
Formula: Al2O3
Corundum var: Sapphire
Formula: Al2O3
Elbaite
Formula: Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
'Garnet Group'
Formula: X3Z2(SiO4)3
Kyanite
Formula: Al2(SiO4)O
Quartz
Formula: SiO2
Quartz var: Amethyst
Formula: SiO2
Spinel
Formula: MgAl2O4
Topaz
Formula: Al2(SiO4)(F,OH)2
'Tourmaline'
Formula: A(D3)G6(T6O18)(BO3)3X3Z
Zircon
Formula: Zr(SiO4)

List of minerals arranged by Strunz 10th Edition classification

Group 4 - Oxides and Hydroxides
Chrysoberyl4.BA.05BeAl2O4
var: Alexandrite4.BA.05BeAl2O4
Corundum4.CB.05Al2O3
var: Sapphire4.CB.05Al2O3
Quartz4.DA.05SiO2
var: Amethyst4.DA.05SiO2
Spinel4.BB.05MgAl2O4
Group 9 - Silicates
Andalusite9.AF.10Al2(SiO4)O
Beryl9.CJ.05Be3Al2(Si6O18)
Elbaite9.CK.05Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
Kyanite9.AF.15Al2(SiO4)O
Topaz9.AF.35Al2(SiO4)(F,OH)2
Zircon9.AD.30Zr(SiO4)
Unclassified Minerals, Rocks, etc.
'Almandine-Pyrope Series'-
'Garnet Group'-X3Z2(SiO4)3
'Tourmaline'-A(D3)G6(T6O18)(BO3)3X3Z

List of minerals arranged by Dana 8th Edition classification

Group 4 - SIMPLE OXIDES
A2X3
Corundum4.3.1.1Al2O3
Group 7 - MULTIPLE OXIDES
AB2X4
Chrysoberyl7.2.9.1BeAl2O4
Spinel7.2.1.1MgAl2O4
Group 51 - NESOSILICATES Insular SiO4 Groups Only
Insular SiO4 Groups Only with cations in >[6] coordination
Zircon51.5.2.1Zr(SiO4)
Group 52 - NESOSILICATES Insular SiO4 Groups and O,OH,F,H2O
Insular SiO4 Groups and O, OH, F, and H2O with cations in [4] and >[4] coordination
Andalusite52.2.2b.1Al2(SiO4)O
Kyanite52.2.2c.1Al2(SiO4)O
Insular SiO4 Groups and O, OH, F, and H2O with cations in [6] coordination only
Topaz52.3.1.1Al2(SiO4)(F,OH)2
Group 61 - CYCLOSILICATES Six-Membered Rings
Six-Membered Rings with [Si6O18] rings; possible (OH) and Al substitution
Beryl61.1.1.1Be3Al2(Si6O18)
Six-Membered Rings with borate groups
Elbaite61.3.1.8Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
Group 75 - TECTOSILICATES Si Tetrahedral Frameworks
Si Tetrahedral Frameworks - SiO2 with [4] coordinated Si
Quartz75.1.3.1SiO2
Unclassified Minerals, Mixtures, etc.
'Almandine-Pyrope Series'-
Chrysoberyl
var: Alexandrite
-BeAl2O4
Corundum
var: Sapphire
-Al2O3
'Garnet Group'-X3Z2(SiO4)3
Quartz
var: Amethyst
-SiO2
'Tourmaline'-A(D3)G6(T6O18)(BO3)3X3Z

List of minerals for each chemical element

HHydrogen
H TopazAl2(SiO4)(F,OH)2
H ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
LiLithium
Li ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
BeBeryllium
Be ChrysoberylBeAl2O4
Be BerylBe3Al2(Si6O18)
Be Chrysoberyl (var: Alexandrite)BeAl2O4
BBoron
B ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
B TourmalineA(D3)G6(T6O18)(BO3)3X3Z
OOxygen
O Corundum (var: Sapphire)Al2O3
O TopazAl2(SiO4)(F,OH)2
O ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
O SpinelMgAl2O4
O Garnet GroupX3Z2(SiO4)3
O ChrysoberylBeAl2O4
O AndalusiteAl2(SiO4)O
O BerylBe3Al2(Si6O18)
O KyaniteAl2(SiO4)O
O Chrysoberyl (var: Alexandrite)BeAl2O4
O Quartz (var: Amethyst)SiO2
O ZirconZr(SiO4)
O TourmalineA(D3)G6(T6O18)(BO3)3X3Z
O QuartzSiO2
O CorundumAl2O3
FFluorine
F TopazAl2(SiO4)(F,OH)2
NaSodium
Na ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
MgMagnesium
Mg SpinelMgAl2O4
AlAluminium
Al Corundum (var: Sapphire)Al2O3
Al TopazAl2(SiO4)(F,OH)2
Al ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
Al SpinelMgAl2O4
Al ChrysoberylBeAl2O4
Al AndalusiteAl2(SiO4)O
Al BerylBe3Al2(Si6O18)
Al KyaniteAl2(SiO4)O
Al Chrysoberyl (var: Alexandrite)BeAl2O4
Al CorundumAl2O3
SiSilicon
Si TopazAl2(SiO4)(F,OH)2
Si ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
Si Garnet GroupX3Z2(SiO4)3
Si AndalusiteAl2(SiO4)O
Si BerylBe3Al2(Si6O18)
Si KyaniteAl2(SiO4)O
Si Quartz (var: Amethyst)SiO2
Si ZirconZr(SiO4)
Si QuartzSiO2
ZrZirconium
Zr ZirconZr(SiO4)

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

Quaternary
0 - 2.588 Ma



ID: 3311842

Age: Pleistocene (0 - 2.588 Ma)

Lithology: Sedimentary

Reference: Thiéblemont, D. (ed.). New edition of the 1:10,000,000 geological map of Africa. CGMW-BRGM. [190]

Jurassic
145 - 201.3 Ma



ID: 3189234
Mesozoic sedimentary rocks

Age: Jurassic (145 - 201.3 Ma)

Lithology: Sedimentary rocks

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License

References

Sort by

Year (asc) Year (desc) Author (A-Z) Author (Z-A)
Schmetzer, K.(1999): Rubine und verschiedenfarbige Saphire aus Ilakaka, Madagaskar. Lapis 24(6), 46-47.
Schmetzer, K., Glas, M. & Bernhardt, H-J. (2002): Sterngranate aus Madagaskar. Lapis 27 (2), 20-27
Hogg, Jonny (2007): Madagascar's sapphire rush. BBC News, 17 November 2007.
Giuliani, G., Fallick, A., Rakotondrazafy, M., Ohnenstetter, D., Andriamamonjy, A., Ralantoarison, T., Rakotosamizanany, S., Razanatseheno, M., Offant, Y., Garnier, V., Dunaigre, C., Schwarz, D., Mercier, A., Ratrimo, V., and Ralison, B. (2007): Oxygen isotope systematics of gem corundum deposits in Madagascar: relevance for their geological origin. Mineralium Deposita 42, 251-270.

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