DIAMOND GRADING & THE 4 C’S

ダイヤモンドの4Cとグレード

Perfectly clear, flamboyant brilliance – this aptly describes the diamonds born from TASAKI’s pride in the pursuit of absolute perfection. World class cutting technology ensures a brilliance unlike any seen before.

Cut

TASAKI cutting technology – changing the standard in diamond grading

The cut is the only process in the creation of a diamond from the natural stone left up to the skill and craft of man. The stunning brilliance of a diamond relies upon the skill and craft of the diamond cutter.
One of the most common cuts is known as the round brilliant cut. The grade of a diamond is determined based on the proportions (general evaluation of the cut), polish, and symmetry with ‘Excellent’ ranking at the very top.
For example, there are 57 facets that can be cut in an accurate diamond cut. At TASAKI, we do not simply cut the culet to create 58 facets, but employ a cutting technology to create the TASAKI BRIDAL diamond.
With this technology, TASAKI has succeeded in the mass production of Excellent grade diamonds in a global market where it is difficult to place above the grade of Very Good, and has grown into a leader in the diamond industry. TASAKI has since improved this technology, achieving a grade of 3EX for 100% of the diamonds cut by TASAKI in a round brilliant cut.

TASAKI Triple Excellent Cut

The grade of a diamond is determined based on the proportions (general evaluation of the cut), polish, and symmetry with ‘Excellent’ ranking at the very top.
A 3EX (triple excellent) is a diamond that has been cut with superior craftsmanship and achieves a grade of Excellent in its proportions, polish and symmetry and the supply of these stones, the ultimate in diamonds, is limited. All of the diamonds cut and polished at TASAKI achieve the grade of 3EX.

Three Elements of the TASAKI Triple Excellent Cut

Only diamonds that achieve a grade of Excellent in proportions, polish and symmetry can be given the grade 3EX.
In addition to the GIA standards, TASAKI triple excellent cut diamonds must pass stringent standards established exclusively by TASAKI for proportions, polish and symmetry and achieve the optimum balance in brilliance, fire and scintillation through superior craftsmanship.

Clarity

Perfectly clear, totally pure. Absolute beauty

Clarity is determined by a specialist using a 10X magnification loupe under good lighting. Diamonds with no discernable inclusions or blemishes that interfere with the passage of light through the diamond receive the grade FL (flawless) with 11 grades following depending on the number of inclusions. TASAKI BRIDAL uses only diamonds achieving a grade of VS2 or above.

TASAKI Clarity Grading

TASAKI has established its own unique and very detailed quality standards. For example, borderline stones are graded on the lower side of the line. This makes it easier to achieve a greater degree of conformity and establish a stable grading system where our stones won’t be downgraded when compared to other external evaluators.

Diamonds Rejected by TASAKI BRIDAL

Diamonds Rejected by TASAKI BRIDAL
Diamonds Rejected by TASAKI BRIDAL

Carat

Testimony of brilliance

Carat is a unit used to determine the weight of a diamond. 1 carat is equivalent to 0.2g.
In general, the higher the carat the more valuable the stone however the value of a diamond is not determined based on carats along. The beauty and value of a diamond is based upon on a combination of the four Cs: Cut, Clarity, Carat and Color.

Specific gravity

The weight (carat) of round brilliant cut diamonds can vary significantly even when they have the same diameter. For example, if we increase the size of the girdle as shown in the figure to the right, the carat will increase 16.4% however at the same time, a surprising amount of brilliance is lost.
At TASAKI we believe that round brilliant cut diamonds shouldn’t be heavier than they look and these kinds of diamonds are rejected from the TASAKI BRIDAL range.

Color

Even the smallest amount of clouding is unacceptable. Color-free, transparent perfection

The best color for a diamond is no color at all and nearly totally transparent, and the closer to this condition the diamond is the rarer it becomes.
The color in white diamonds is rated in 23 grades from D (colorless) to Z depending on the tinge of yellow in the stone. Only diamonds equal to or above the grade of H (near colorless) are used in the TASAKI BRIDAL range.

Fluorescence

There are diamonds that when subjected to ultraviolet light (such as a black light) will absorb the ultraviolet light and emit a soft glow. While fluorescence is a natural phenomenon appearing in approximately 60% of all diamonds it will make diamonds appear cloudy under natural light and effects overall brilliance.
TASAKI inspects all its diamonds for fluorescence in their rough state and will not use stones with noticeable fluorescence (Strong or above), even under natural light.