Diamond Trivia

What are Diamonds?

With their everlasting brilliance, diamonds are said to be the hardest substance of all the world’s natural minerals. An allotrope of carbon, besides their use as adornments, they are used as abrasives and have many industrial applications. Diamond powder is also used to cut and polish diamond gemstones.

Asset Value of Diamonds

The quantity of diamonds distributed on the market is controlled by the Central Selling Organization, which is run by De Beers, the world’s largest diamond company. Even compared with metals such as gold and platinum, there is relatively little fluctuation in the market value of diamonds, which makes them noteworthy not only for their value as adornments, but also as assets. Eiwa Boueki procures good quality stones directly from sightholders in Israel and Belgium.

Diamond Grading Criteria

There are four criteria for grading diamonds, known as the 4C’s.

3EX Excellent Very Good Good Fair Poor

Cut is the most important element of the “brilliance” that determines the beauty of a diamond. This is the only aspect of diamond grading in which the value can be changed by the work of human hands. The “round brilliant cut” is said to be the shape that most draws out the beauty of a diamond. This cut is round, and has a total of 58 facets – 33 on the crown and 25 on the pavilion. Eiwa Boueki is particularly committed to this cut. The highest grade for cut is 3EX (Triple Excellent). Achieving this grade is extremely difficult, and while all diamond cutters aspire to 3EX when cutting diamonds, about half of them only achieve the lower grades of EX (Excellent) or Very Good. This, of course, results in a lower value being placed on the diamond. Eiwa Boueki possesses some of the highest-class diamond cutting skills not only in Japan, but in the world, and has achieved the top cut grade of 3EX in almost 100% of the diamonds it cuts. It also has patents for as many as 16 types of cut.


The cut diamonds are inspected by an expert using a specialist magnifying glass at a magnification of 10x. Clarity is determined by where or not there are inclusions in the diamond, and, if they are present, the location, size, nature, number, and color of those inclusions.
There are 11 grades, ranging from I-3, in which inclusions are visible to the naked eye, up to the top grade of “flawless” (FL).


Color, as the name suggests, indicates the color of the diamond. The less color in a diamond the higher its quality, with the best quality indicated by the letter “D.” Diamond color is compared against master stones from the GIA (Gemological Institute of America), and is rated in 23 grades from D to Z depending on the tinge of yellow in the stone.


The weight of diamonds is indicated by the number of carats. One carat is equivalent to 0.2 grams, and is indicated with the unit “ct.” The higher the carat, the higher the rarity of the stone. Diamonds with the same number of carats will have different brilliance and value according to differences in cut and other aspects of quality. For clean shapes, the number of carats can generally be determined by the following formula.
Diameter x diameter x depth x 0.0061 = ct