Emerald carat weight refers to an emerald's weight, not size. Emeralds weigh less than diamonds, so a 1-carat emerald cut in the same shape and proportions as a 1-carat diamond will look larger than the diamond because it is lighter in weight.

Similarly, due to exceptional formations of emeralds in Colombia, their mines produce emeralds lighter in weight than emeralds found in other parts of the world. This means that a 1-carat Columbian emerald appears larger than emeralds found elsewhere - everything else being equal.