Difference between revisions of "Maxixe"

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The impurities found in Maxixe and Maxixe-type Beryl are Cs, Zn, Li, Rb, B and high concentrations of Fe.
 
The impurities found in Maxixe and Maxixe-type Beryl are Cs, Zn, Li, Rb, B and high concentrations of Fe.
  
As the color is mainly caused by a color center, this is not an Aquamarine Beryl but a variety on its own.
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As the color is mainly caused by a color center, this is not an Aquamarine Beryl but a variety on its own.<br />
 +
Both the nitrate and carbonate varieties can be irradiated by natural and artifical means and their distinction is not possible with standard gemological instruments, therefor Kurt Nassua suggested to drop the Maxixe-type nomenclature and name both Maxixe.
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Maxixe and Maxixe-type Beryl has stronger dichroic colors in the ordinary ray, while Aquamarine has the stronger dichroic
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color in the extra-ordinary ray. Classification based on this is not viable as [[Heliodor]] may also have the stronger dichroic color in the ordinary ray.
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==Sources==
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* ''On the identification and fade testing of Maxixe beryl ..'' - Kurt Nassua, The Journal of Gemmology (April 1996)

Revision as of 08:11, 26 October 2006

Maxixe beryl
Chemical composition Be3Al2(SiO3)6 Beryllium aluminum silicate
Crystal system Hexagonal
Habit Prismatic
Cleavage Poor, basal
Fracture Conchoidal to uneven
Hardness 7.5
Optic nature Uniaxial -
Refractive index 1.579 - 1.592
Birefringence 0.007
Dispersion Low, 0.0014
Specific gravity 2.69 - 2.8
Lustre Vitreous
Pleochroism Distinct

Maxixe (pron. Mah-she-she) is the almost Sapphire color variety of Beryl. It was discovered in 1917 in the Maxixe mine in the Piaui area south of Arassuahy, Minas Gerais, Brazil. Maxixe owes it's very unstable color due to natural irradiation which causes a color center that is most probably in the NO3 sites. When exposed to sunlight or temperatures above 100° C. it will rapidly loose its color, which can be restored by irradiation (gamma, x-ray or neutron) and annealing.
As of 1973 some dark-blue Beryls started appearing on the market again and research showed that the color was also due to irradiation (artificial), the color center in this case proved to be in the CO3 sites. This new type was named "Maxixe-type" Beryl and like Maxixe it is a very unstable color. The starting color of these stones were yellow or green Beryls.
There are also bi-colored Maxixe-type Beryls (yellow/blue) and their color is attributed to artificial irradiation on specimens that have uneven distribution of impurities.

The impurities found in Maxixe and Maxixe-type Beryl are Cs, Zn, Li, Rb, B and high concentrations of Fe.

As the color is mainly caused by a color center, this is not an Aquamarine Beryl but a variety on its own.
Both the nitrate and carbonate varieties can be irradiated by natural and artifical means and their distinction is not possible with standard gemological instruments, therefor Kurt Nassua suggested to drop the Maxixe-type nomenclature and name both Maxixe.

Maxixe and Maxixe-type Beryl has stronger dichroic colors in the ordinary ray, while Aquamarine has the stronger dichroic color in the extra-ordinary ray. Classification based on this is not viable as Heliodor may also have the stronger dichroic color in the ordinary ray.

Sources

  • On the identification and fade testing of Maxixe beryl .. - Kurt Nassua, The Journal of Gemmology (April 1996)