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A study of  MULTICOLOR TOURMALINE

 

Multicolor ribboned tourmaline cabochon, red green white pink Madagascar tourmaline, exclusive tourmalines, color tourmaline information data
Discover:

The Ribboned Tourmaline !

Tourmaline, mixed crystals of aluminium boron silicate with a
complex and changing composition, shows a variety of colors
and designs may be unique in gemstones.
The mine of Alakamisy Itenina in the highlands of Madagascar, 
was discovered in 1989 in a rice plantation.
The tourmaline deposit is alluvial and the shape of the stones 
remains rolled.
This occurrence is hand worked and the stones are at a depth 
ranging from a few meters up to twelve meters.
©  Image J. Darbellay
Atomic Bonding.

In minerals, atoms bind together to form molecules through their orbital of higher energy, i.e. that only the outer layers of electrons involved. They are the ones who also, by electromagnetic excitation, will be responsible for the color. The links can be of four types: covalent, ionic, metallic, and of Van der Waals.

Pair Multicolor tourmaline cabochon, red green white pink black Madagascar tourmaline, exclusive tourmalines, color tourmaline information dataPolychrome ribboned tourmaline cabochon, red green white pink Madagascar tourmaline, exclusive tourmalines, color tourmaline information dataMulticolor ribboned tourmaline double table, red green white pink Madagascar tourmaline, exclusive tourmalines, color tourmaline information data
Sawing a Multicolor ribboned tourmaline slice in Madagascar, red green white pink Madagascar tourmaline, exclusive tourmalines, color tourmaline information data

Sawing a large block of tourmaline in Madagascar, using a diamond blade.
The metal disk must be continuously humidified by a jet of water in order to lower its temperature.

Tourmalines have a complex structure featuring various 
polyhedral environments for cations and which allow many 
substitutions for elements as common as iron, titanium, 

Growth zoning in a  tourmaline from Alakamishy Itenina.

manganese, magnesium, lithium, chromium, etc.. under their 
valences. 
The tourmalines group represents a privileged field of 
investigation. By themselves, the aforementioned metals, 
commonplace in the earth's crust, can account for all the
colors observed.
    We will keep this very telling example about the pink color
which involved both a electronic colorful center and a color free
center. The work by K. Nassau on a large number of specimens
treated by irradiation and heating indicates the existence of at
least seven different pinks. I.e. at the place where our eye can 
only see a pink shade, measuring devices detect seven distinct 
causes.
Pair Multicolour tourmaline cabochon, red green white pink Madagascar tourmaline, exclusive tourmalines, color tourmaline information data
The thickness of a ribboned polychrome
tourmaline cabochon usually reaches 3.5 to 
5.5 mm. depending on the size of the stone.
Wavelength:
Physics knows wavelength of radiation only, the notion of color is completely 
foreign to it. That's why it is so helpful to us in the interpretation of color in 
minerals. A spectrograph that only identifies the position of spectral lines will 
perfectly make the difference between a radiation at 0.530 microns and an another 
at 0.532 microns, where our eyes will only receive the same green.
Reinitz shows that the pink color of tourmalines from many fields is the result
of a continued natural irradiation. During their growth, these tourmalines
incorporate Mn2+ whereas initially they are by nature very pales. Their
granitic environment imposes to them a natural gamma ray exposure due to
radioactive decay of 40K causing the gradual formation of the Mn3+, ions
responsible for pink color to red.
Some elbaites show that copper is their main coloring agent. Copper alone is
responsible for two strong absorption bands around 695 and 940 nm that give
a turquoise-blue. An additional absorption at 515 nm, attributed to Mn3+,
produce a shift towards purple. A broad absorption centered in the ultraviolet
and extending into the visible range, causing a drift towards more green
shades when combined with the absorption due to Cu2+.
Ribboned Tourmalines Cabochon
   
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    Alain Darbellay © All of the pictures on this website have been shot by gggems.com
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