There are a number of differences between Colombian emeralds, Brazilian emeralds, and Zambian emeralds. Price is the first thing to consider when choosing the country of origin of emerald you want to buy. Colombian emeralds will typically be the most expensive per carat followed by Brazilian emeralds and lastly Zambian emeralds. The reason for this is due to color. Colombian emeralds get their color primarily from the trace amounts of the element chromium. Chromium produces some of the purest green hues in gemstones. Brazilian emeralds get their color primarily from trace amounts of the element vanadium while Zambian emeralds get their color from iron. Brazilian emeralds typically have a slight brown or gray cast and only sometimes match the pure green hue that many Colombian emeralds offer. Zambian emeralds often appear too blue due to the iron content. In reality though emeralds from all three countries can be colored by more than one element.
The type and number of inclusions found in emeralds also varies by country. Colombian emeralds tend to have more inclusions than either Brazilian or Zambian emeralds. As the chromium content increases producing a deeper green hue the number of inclusions tends to increase also. Zambian emeralds generally are the least included of the three major emerald producing countries.