This very nice pink emerald cut has its tone level grade smoothly down the length of the gemstone. The tone gradation, without a hue (color) shift could be caused either by an increase in concentration of manganese in the darker tone areas or the manganese could be in a higher oxidation level. Mn+3 is a much stronger chromophore (coloring agent) than Mn+2. The possibility of a higher oxidation level for manganese would probably be caused by natural radiation. Even without the chemistry this gemstone would make a great ring stone. It weighs 1.51 carats and is clean with great crystal. A flasher all the way around.