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Diamond Carat Weight

For many people, bigger is better when it comes to their diamond jewelry. This is why, when you come to Joseph Jewelry’s custom jewelry design business in Seattle and Bellevue, it is good to be familiar with the concept of carat weight.

What is carat?

Carat is a special unit of weight reserved for precious stones and pearls. It is not to be confused with karat, which refers to gold purity (18KT gold, for example). These measurements are not related.

What are the origins of the carat system?

First spoken in English in the mid-15th century, the word carat came from Italian carato, which came from Greek kerátion, meaning carob seed. In the old world, the carob seed was a close match to diamond size, and the seed was easy to find and use. These seeds were uniformly chosen in size and shape to be used on a balance scale against diamonds or other gemstones. The current weight measurement, known as the metric carat, was adopted in 1907 at the Fourth General Conference on Weights and Measures and soon after, many countries around the world followed suit.

Modern scales use the metric carat weight: 1 carat is equal to 200 milligrams. The carat is divisible into one hundred points of two milligrams per point. For example, a 25 point diamond weighs .25 carats, or 50 milligrams (also referred to as a quarter carat). Other subdivisions, and slightly different mass values, have been used in the past in different locations around the world, but today carat weight is the international method used to weigh diamonds and other gemstones.

How does carat weight affect price?

Diamonds are extremely rare. Thus, precise weighing scales are crucial. If a diamond weighs 300 points, or 3.00 carats, at a price of $80,000, that means 1 point costs $267. A 1 point difference is hardly visible to the naked eye. To find an accurate measurement of diamond weight, professional diamond scales are used. Most scales cost over $2,500 each due to the quality and precision of the instruments.

When pricing a 1 carat diamond, the price is much less per carat compared with a 2 carat diamond of the same quality. This is because high carat diamonds are much rarer as they grow in carat. For example, a 1 carat diamond might cost $7,500 (depending on the market price). However, the same quality 2 carat diamond will not be double the cost at $15,000. This is because the rough material needed to produce a 2 carat diamond is much harder to find, so this diamond will be priced around $25,800. Notice how the price increased exponentially: this is because a considerable amount of rough material must be mined to produce a 2 carat diamond. In this case, over two million diamonds could be extracted from the ground to find that single 2 carat diamond.

Diamond cutters are trained to preserve the highest weight possible when cutting rough diamonds, using the threshold marks as their goal. When most people think of diamond weight, they think .25 carat, .50 carat, .75 carat, 1.00 carat, 1.25 carats, and so on. These are called threshold marks. However, many cut diamonds fall short of the threshold mark; if a crystal should yield approximately 1.00 carat but the cutter ends up with .90 carat, this diamond will sell for less per carat price than if it was 1.00 carat. Suppose you are looking at a 1.00 carat diamond [G VS2] but can’t afford it. Consider a .90 carat [G VS2]. It is .10 carat smaller, but the price per carat drops significantly while the size is very similar. Only an expert can tell the difference. In reality, there are many diamonds that fall short of the threshold mark, such as .20 to .24 carat, .26 to .49 carat, and so on. These diamonds will sell for less per carat, leaving the consumer with an opportunity to save while maintaining approximate desired size.

What does shape have to do with price?

Round diamonds are more expensive than other shapes. This is due to the cutting process: round cut diamonds lose more rough material during cutting than other shapes. This is also true when cutting diamonds to Excellent grades, Ideal grades or Star129 diamonds. In these cases the cutter focuses on producing the perfect cut diamond, and not the weight preservation or threshold, thus losing even more rough material until the desired cut is reached. A diamond deserving of Triple Excellent grade or Triple Ideal grade requires the best cutters in the industry and a large starting amount of rough material. If you are looking for a diamond that appears larger, consider browsing emerald or marquise shaped diamonds.

Joseph Jewelry Shopping Tips:

• No matter what the carat weight of the diamond may be, the best value can be obtained through a diamond in the ranges of F to I in color and VS1 to SI1 in clarity, with the weight of the diamond outside the threshold mark. This variety of choices give you leverage to control the price to fit your budget.

• Do not sacrifice cut for carat. A 1 carat round diamond cut to Triple Ideal or Triple Excellent proportions should have diameter measurements of 6.3mm to 6.5mm. If you come across 6.2mm or less, that means the diamond is cut too deep, making the diamond inferior when it comes to brilliance and light performance. If you come across a diamond measuring 6.7mm or more in diameter, the diamond is cut too shallow. One of the reasons we recommend Triple Ideal or Triple Excellent cut diamonds is to avoid guessing measurements when it comes to the quality of proportions, since Triple Ideal or Triple Excellent are certified by independent laboratories as the perfect proportions.