So they say, you must have at least one diamond in your lifetime. If you can afford another one, then a two or three won't hurt. Here are some facts you need to know about picking up the finest diamonds. I'll start with Carat.
CARAT means weight (1 carat = 1/5 of a gram) A diamond weight is a very important factor to its cost. The term "carat " originated from the seeds of the carob tree. These carob seeds are extremely uniform in eight and this made them the ideal weight unit for the ancient gem traders. This weight (one carob seed) as later standardized to be 1 carat, or 1/5th of a gram, hence a five carat diamond equals 1 gram and 155.51 carats equal one ounce.
The one carat weight is then broken down into 100 equal parts called "points"; 75 points equal 3/4 of a carat, 50 points equal 1/2 of a carat, etc. The significance of the weight is like the other quality grades. Rarity, now by virtue of the diamond's size and weight. Out of 250 tons of diamond ore only a single one carat diamond of gem quality may be found. The value of weight a 100 point (1 full carat) diamond of VS-1 clarity and G body color is generally worth more than an identical VS-1, G color diamond with a weight of .99 carats (less than a full carat). A one point difference in a diamond can make a difference in value.
It is important to understand that the weight of a diamond and its physical size are two different things. Even if the only difference between the two diamonds is .01 carat. Take for example two (2) VS-1, G quality grade 1.00 carat diamonds to show the vast difference in value that the cut will make. One of these diamonds could have the Ideal 6.5 millimeter diameter size one would expect to see in for a 1.00 carat diamond. In the other example, the second 1.00 carat diamond may have only a 5.5 millimeter diameter. Because of this one millimeter diameter size difference, and yet the same carat weight, the smaller diameter diamond would be worth somewhere around 20% less than the Ideal cut diamond of the same weight and quality grade.
These value differences will vary depending upon the size and quality grade of the diamond you may be interested in. This leads us to the fourth quality grade which is the diamond cut. Every Diamond belongs in a weight grouping class for a range of weight where the prices per carat for each Color and Clarity group combination are listed. The main reason for this is obviously due to rarity in nature, but current market conditions at any specific time plays a very important role. Some sizes and shapes fall in and out of demand due to what is fashionable or considered affordable in society. Because of this, some size groupings for a given shape may have a higher demand and price per carat than one expects, given its rarity in nature.
So to simplify, a diamond in the 1 carat class (1.00-1.49) usually costs more per carat than a diamond less than 1 carat in weight (0.90-0.99). A diamond that is 1 full carat in size, has a higher demand, which causes it to be priced higher. The result is rough stones that could possibly have been cut into beautiful smaller stones are usually cut into not so beautiful 1 full carat stones to get into the higher price range. There are other factors and trade-offs this is just a simplified answer to the reason the cost per carat goes up as the size goes up.
