The astrological effects of a natural emerald will depend largely on its colour, clarity, carat weight. Till these parameters are being met, original emeralds from any mine will give good results. Hence, for top quality emeralds, Colombian and Zambian ones give similar results. However, in lower grade emeralds, one may be caught between selecting a light-coloured Colombian emerald and a dark Zambian emerald. In that case, Colombian will be preferable as it is likely to be purer green with nearly no bluish tints and display comparatively high clarity which altogether assists its astrological properties. The Zambian emerald
may be darker but lacks purity in green hue due to the slightly bluish or black overtones. Additionally, it may have lower transparency and some unwanted inclusions. If the Zambian emerald does not have these problems, then the Zambian emerald would be better. In 90% cases though, it probably suffers from one of those issues, and hence the lighter Colombian emerald may be a better choice to go with. The difference, however, is not significant, so if you feel strongly about one particular origin, go ahead with that!