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                                             Crystalline System: cubic.
Red - violetish: Hardness Density Ref.Index
Pyrope    Mg3Al2Si3O12 7,25 3,58 g / cm3 1,714
Almandine Fe3Al2Si3O12 7,50 4,32 1,830
Rhodolite Mg,Fe3Al2SiO12 7,25 3,78 - 3,90 1,74-1,78
Orange - yellow-brown :
Spessartite Mn3Al2Si3O12 7,25 4,20 - 4,25 1,78 - 1,81
Malaya       Mn3Al2(SiO4)3 7,25 3,74 - 4,00 1,78
Hessonite   Ca3Al2(SiO4)3 7,25 3,58 - 3,65 1,73 - 1,74
Green :
Tsavolite     Ca3Al2(SiO4)3 7,25 3,60 - 3,68 1,73 - 1,74
Uvarovite     Ca3Cr2Si3O12 7,50 3,85 1,87
Dementoïde Ca3F2SiO12 6,5 - 7 3,82 - 3,85 1,89

In a perfect crystal, when a face appears in the crystal in the process of growth, all the faces appear with 
the same development.
If one of the symmetrical faces is less developed on a crystalline sample, or exceptionally does not 
appear, that comes from the accidental actions of the external environment which opposed its growth.
Temperature, pressure, nature of the mineral solution, speed of the crystalline growth and the direction of 
the movement of solution etc... represent the external influences on the crystalline forms.
The frequency of the faces of the crystals is related to the reticular density, the fast growth of some faces
influences the crystalline form definitively.
Garnet thus crystallizes under the cubic system, whose crystals are characterized by the presence of 
three quaternary axes A4 joining the centers of the faces, four ternary axes A3 joining the opposed tops, 
six binary axes A2 joining the mediums of the edges.
· One of the causes modifying the initial form of crystals is truncation.
Truncation on corners.
Cube Dodecahedron
Truncation cuts two different lengths on adjacent corners.
Cube Tetrahexahedron
Truncation cutting three equal lengths out of the three adjacent corners.
Cube Octahedron
Truncation cuts two equal lengths out of two corners and a larger length on the third.
Trisoctahedron Octahedron
Truncation on the segment crosses, two equal lengths out of two corners, a smaller length on the third.
Cube Trapesohedron
Octahedron Trapesohedron
Dodecahedron Trapesohedron
Hexoctahedron Dodecahedron
Almandine in matrix Pyrope-Almandine Almandine in matrix
Almandine in matrix Almandine in matrix Rhodolite (Ambohitompoina)
There is also a law according to which certain crystals do not present modifications that on half of corners, 
or of the similar angles.
Here is a truncation on a top cutting three different lengths on corners, and which repeats only three
times around the ternary axis.
Cube and diplohedron Diplohedron Right Gyrohedron  Left Gyrohedron
The diplohedron is made of twenty-four irregular quadrilaterals. The class plagiohedron whose faces (HKL)
are arranged in the spiral order. 
In other cases, twelve irregular pentagons are formed by a truncation on one sharp angle, on both adjacent 
angles, the unequal lengths, it is the pentagonal dodecahedron.  
Positiv  Négativ
Almandine in matrix Tsavolite (Madagascar) Spessartite in pegmatite
The regular tetrahedron consisted four equilateral triangles forming between them an angle of 70° 31.
Positiv tetrahedron  Négativ tetrahedron Octahedron
 Positiv tetrahedron Cube
The tetrahedron or triakistetrahedron consisted twelve faces which are isosceles triangles, and the 
hexatetrahedron  with its twenty four triangular faces. 
Triakistetrahedron Hexakistetrahedron
The trapezoidal dodecahedron consisted twelve quadrilaterals deltoïde and the tetrahedral pentagonal 
dodecahedron are formed by a truncation appearing on each top and cutting three different lengths on 
  right left
Deltoïde dodecahedron Pentagonal tetraedrical dodecahedron . Almandine in matrix
Spessartite (Ambohimarangitra) Malaya  (Andoharano) Malaya  (Madagascar)
Rhodolite  (Ankilytokana) Hessonite  (Soakibany) Imperial Malaya  (Madagascar)
In Madagascar, one finds rhodolite in a gneiss rich in biotite, in which (almandite-pyrope) is presented in 
the form of small grains, or with the state of large porphyroblasts, generally deprived of geometrical 
contours, plagioclase(oligoclase with andesine) is the feldspar dominating and sometimes exclusive. 
These gneisses contain sometimes pegmatic beds very rich in crystals.
One very finds also garnetiferous gneisses containing little biotite, hardly directed.
Kinzigites. The gneisses which have been just enumerated have a very clear schistous structure, which 
had with the biotite abundance. A rather frequent type is approximately blocks and presents a compact 
aspect, thanks to the prevalence of large garnets without geometrical form, associated quartz and feldspar 
granoblastic, biotite is not very abundant. The structure points out that of corneal micaceous of contact of 
the granite. This gneiss can be compared with the kinzigite of the Black Forest. 
Leptynites with amphibolo-pyroxenite intercalation rich in garnets of a pale pink (almandite-pyrope), with 
often rutile and graphite abound in certain areas of Madagascar. The feldspar is orthoclase, associated 
with ogigoclase-albite feldspar and sometimes with spindle-shaped microperthite, there exists much of myrmekite.
These rocks are with fine grins, but they very often contain large regularly distributed crystals.
Usually garnet does not have a geometrical form, but it takes clear faces in more quartzose zones.
Leptynites derive from the granites by disappearance of the mica; the garnetiferous mica schists 
constitute the opposed pole in which biotite prevails, with progressive disappearance of feldspar. 
  The Besafotra river carry the 
  spessartites onseveral kilometers 
  from their source, doubtless a 
  sodolitic pegmatite. A walk of 25 
  kilometres among the mountains is 
   necessary to reach this place. 
The tanety "grounds bordering the river," are also
the object of the orange garnet's fever. 
Sifting in river.
Initially, the spessartite appeared in 
the Besafotra river, searched out 
here near to its source. 
Ankilytokana, one of the fabulous rhodolite deposit 
exploited in a leptynite vein on a sixteen 
meters depth. 
Leptynites are primarily consisted in alkaline feldspars 
and quartz. When these rocks are not ribboned, and 
that is frequent, it is often difficult to decide if a  
sample, not seen in place, belongs to a leptynite or an 
aplite, it should be noticed that in Madagascar, these 
last contain microcline and not of orthoclase. In this 
area, one observes graphite spangles in the leptynites.
 Malaya garnet discovered into
 September 1998, in eluvium in
 a broken up leptynite.
 The modest depth of the deposit 
  did not require a significant work 
  to extract it.
This stone shows an exceptional capacity to restore 
the light, thanks in particular to its high refractive 
index, especially under not very enlightened condition.
  All of the pictures on this site have been shot by Darbel du Bourg.

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