Vanadium Beryl

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Emerald
Chemical composition Be3Al2(SiO3)6 Beryllium aluminum silicate
Crystal system Hexagonal
Habit Prismatic
Cleavage Imperfect, basal
Fracture Conchoidal to uneven
Hardness 7.5 (brittle)
Optic nature Uniaxial -
Refractive index 1.566 - 1.600
Birefringence 0.004 - 0.010
Dispersion Low, 0.014
Specific gravity 2.67 - 2.78
Lustre Vitreous
Pleochroism Weak to distinct

There are two schools of thought concerning whether green beryl colored by vanadium should be considered an emerald or not. The GIA considers it to be so, Gem-A does not. Up until about 40 years ago, no one considered vandium beryl to be an emerald, despite known deposits such as those in Afghanistan and Pakistan. The Chelsea filter was developed specifically to separate emerald from vanadium beryl, as the chromium content in an emerald will make it appear red under the filter while the vanadium stones are inert.

In the early 1960's, large deposits of vanadium beryl were discovered in Brazil. Much to the frustration of the miners and dealers, the industry refused to consider this material as emerald due to it's lack of chromium content. In 1963, the GIA issued it's first lab report identifying vanadium colored green beryl as emerald. In their curriculum, they now teach that vanadium beryl is emerald.

However this was not accepted by the entire industry, whether they are or aren't still depends on who you are talking to or where you are doing your studies.

Vanadium emeralds tend to be less included than their chromium colored brethren.