Due to their scarcity, emeralds are usually more costly than diamonds. There are, however, many diamonds that are more costly than emeralds of the same carat weight, particularly beautiful colored diamonds. The price is determined by the quality of each particular gem, making precise pricing unattainable without knowing the details of quality. They are also valued differently, despite the fact that they both utilize the 4Cs of color, clarity, cut, and carat weight.
Color is the most important of the 4Cs in emeralds (and any other colored stone), followed by clarity and cut. Carat weight of any diamond is not a measure of quality, but rather of the rarity of the quality that the first three Cs show.
Clarity and Cut
Because clarity and cut contribute to the diamond’s appearance, the 4Cs are equally weighted in diamonds. The round-brilliant cut we know today is derived from the Tolkowsky Cut, which was developed by Marcel Tolkowsky as part of a Ph.D. subject to make diamonds sparkle as brilliantly as possible.
Assuming that the 4Cs of quality for emeralds and diamonds are about equal, beautiful emeralds are much rarer than diamonds. Fancy-colored diamonds are the one exception to this rule. These diamonds account for fewer than 1% of all diamonds on the market and have prices that are prohibitively expensive for anyone but a few very rich people. To give you an idea of how insane these prices may be, the Hope Diamond in the middle below is valued at at least $200 million dollars USD (albeit it is not for sale).
In any case, diamonds account for the majority of the jewelry business. Almost every jewelry case you look at will be mostly comprised of diamond jewelry, perhaps with a few additional stones thrown in for good measure. In many instances, the jewelry is completely made of diamonds. The renowned diamond area on 47th Street in New York City is nearly entirely dedicated to diamonds. However, here is also where gem merchants selling other valuable gemstones such as sapphires, rubies, and emeralds sell their wares. Outside of the gem trade’s specialized areas, anything else is uncommon.