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Tranomaro in 1991  >>
Geographical division
We will distinguish: 
1 the volcanic solid mass of
Androy, it is covered with
thorny bush and meadows.
2 the gneissic zone of to 
Mandrarean Androy, fields
plains and hills, rare zones
of savanna on of red ground  At the time
calcareous carapace.  of the great
Altitude varies there from  dryness in
600 meters on the hills  the south.
to 250 meters at the bottom. 
3 the western slope of the high Anosyans
chains which tops are staged between 
1500 and 2000 meters.  It is a field of 
Geological divisions.  
1 Crystalline schists.  
Gneiss with diopside, syenitic eysies 
gneisses, arteritic injections, gneiss at
cordierite, etc.
2 Old eruptive rocks.  
Pegmatites, Dissogénites, Esirians 
granites , charnockites, kalambatreans 
granites, late granites .
3 Recent eruptive rocks.  
(Volcanic solid mass of Androy)
a)  A the base, a thick basaltic 
subhorizontale series .      
b)  Basaltic dykes.                                                    On the road to Andranondambo
c)  A thick higher subhorizontale rhyolitic series.
d)  Rhyolitic dykes .  
4 Recent formations.  
If russet-red sands are excluded, the recent
formations have only a very weak development.
It is necessary to quote the alluvial plains of 
Androtsy, Esira, Sangoria and Pisopiso.
A notable calcareous carapace covers most of the area.
            Metamorphic dolomitic marble.
The anosyans granites are regarded as synorogenes, eocambrians
formed in the androyans series to which an age higher than 2400 MY 
is allotted.
The esirians granites present very variable crushings of intensity which 
often give them a gneissic facies .
Sometimes, there is passage to orthogneisses. General foliation is sub meridian. 
The occurrences of the Andranondambo area were industrially exploited since 1993 and have been 
almost abandoned few years later. This, because of difficulties to exploit sapphire direct in the
bedrock, usually corundum is not concentrated enough. Furthermore, the hardness of the
rock makes its exploitation very expensive.
Andranondambo Sapphire Discovery
The story
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       Text written by Alain Darbellay.
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