Does the color of the emerald depend on the deposit?
Everyone knows that the green color of an emerald is associated with an admixture of chromium in it. But this green color in stones from one or another deposit has different shades. Let's figure out why.
It's all about additional impurities, the composition and quantity of which directly depends on the type of emerald deposit. So, in addition to chromium color centers in emeralds, there can also be centers of ferrous iron in different coordination, sometimes vanadium and titanium, as well as hole centers O-.
Colombian emeralds are characterized by an almost pure green color, sometimes with a slight blue tint caused by pleochroism. The purity of the color is due to the fact that chromium in such stones is practically the only chromophore due to minimal concentrations or the complete absence of iron impurities.
Ural emeralds have a higher concentration of Fe2 + in tetrahedral coordination, which is the reason for the "warmer" tint of stones from this deposit.
Emeralds from Zambia are characterized by a high concentration of ferrous iron in octahedral coordination and have a blue-green color associated with this color center.
We should also highlight emeralds, colored green thanks to vanadium centers. They are sometimes called "chromeless". This type of stone is found among Colombian emeralds, and this type of color is created when emeralds are synthesized by flux and hydrothermal methods.