DIAMOND QUALITY

The stringent appraisal criteria
and quality of TASAKI diamonds

GRADING

Appraisal criteria of
TASAKI diamonds

The '4Cs' are an international appraisal criteria for diamonds prescribed by the GIA (Gemological Institute of America). TASAKI sends its graders for diamond appraisal and discernment courses at the GIA. Based on the criteria learned there, we set even more stringent in-house standards to ensure that our professionals preserve the TASAKI diamond quality.

The 4Cs international quality criteria of diamonds devised by the GIA

CUT

CARAT

CLARITY

COLOUR

Based on the 4Cs, we set even more stringent in-house standards

TASAKI BRIDAL diamond quality based on original appraisal standards

01 CUT

We use only

3EX

02 CARAT

We use only

0.20ct

or higher

03 CLARITY

We use only

VS2

or higher

04 COLOUR

We use only

H

or higher

01 CUT

The ideal cutting ratio for ensuring maximum light reflection

1. Girdle diameter (100%)
2. Star length (50 - 60%)
3. Table (53 - 58%)
4. Crown angle (33° - 35°)
5. Pavilion angle (40.6° - 41.6°)
6. Lower half length (75 - 80%)
7. Culet
8. Crown height (14.5 - 16%)
9. Girdle thickness
10. Pavilion depth (42.5 - 43.5%)
11. Depth (59.2 - 62.4%)

TASAKI's Ideal Proportions

Proportions are set assuming girdle diameter of 100%.

Names of each part

1. Girdle diameter (100%)
2. Star length (50 - 60%)
3. Table (53 - 58%)
4. Crown angle (33° - 35°)
5. Pavilion angle (40.6° - 41.6°)
6. Lower half length (75 - 80%)
7. Culet
8. Crown height (14.5 - 16%)
9. Girdle thickness
10. Pavilion depth (42.5 - 43.5%)
11. Depth (59.2 - 62.4%)

Close

Grading based on three features with 5 levels each

One of the most common diamond cuts is the round brilliant cut, which is evaluated according to five grades, with the Excellent grade being the highest. The grades are based on three items, namely proportions (general evaluation of the cut), polish (state of surface polish), and symmetry.

Cut: 5 grades

Excellent

Very
Good

Good

Fair

Poor

Achievement of
Top Grade 3EX Cut

By improving our cutting techniques even further, TASAKI went on to achieve a 3EX (Triple Excellent) cut, which represents the top grade in all three of the grading categories mentioned, and we now produce 3EX for 100 percent of the diamonds we cut. Only these 3EX diamonds are used for TASAKI BRIDAL pieces.

3EX cellent

Proportions

General cut appraisal

Excellent

Polish

Surface polishing state

Excellent

Symmetry

Excellent

02 CARAT -Weight

Proportions that balance carat weight with brilliance

Carat, the unit used in measuring
the weight of a diamond

1.50ct
Approx.
7.4mm

1.00ct
Approx.
6.4mm

0.70ct
Approx.
5.8mm

0.50ct
Approx.
5.2mm

0.40ct
Approx.
4.8mm

0.30ct
Approx.
4.3mm

0.20ct
Approx.
3.8mm

Higher carat detracts
from brilliance

A carat is equivalent to 0.2g. Since the girdle diameter is determined in the rough stone stage, at least 10 percent more carats can be obtained by cutting with a thick girdle. However, a surprising amount of brilliance is lost when a diamond is cut with a thick girdle.

Girdle diameter

Depth

Girdle
thickness

Cutting according to
original ideal proportions

TASAKI attaches more importance to maximum brilliance than weight when cutting diamonds according to its own ideal proportions, which are established according to each girdle diameter.

Too shallow

TASAKI IDEAL

Too deep

03 CLARITY -Transparency

Rigorous grading of diamonds

Handling diamonds of
VS2 grade or higher (6 grades)

Diamonds with no discernable inclusions or blemishes interfering with the passage of light through the diamond receive the grade FL (flawless), with 11 grades following, depending on the number and size of inclusions. TASAKI BRIDAL uses only diamonds achieving a grade of VS2 or higher.

FL	Flawless	No internal or external flaws
IF	Internally Flawless	No internal flaws
VVS1	Very Very Slightly Included	Inclusions are difficult to detect at 10X magnification
VVS2
VS1	Very Slightly Included	Inclusions are slightly difficult to detect at 10X magnification
VS2
SI1	Slightly Included	Inclusions can be easily detected at 10X magnification, but are difficult to detect with the naked eye
SI2
I1	Included	Inclusions can be easily detected with the naked eye
I2
I3

Handling diamonds of
VS2 grade or higher (6 grades)

Diamonds with no discernable inclusions or blemishes interfering with the passage of light through the diamond receive the grade FL (flawless), with 11 grades following, depending on the number and size of inclusions. TASAKI BRIDAL uses only diamonds achieving a grade of VS2 or higher.

Stringent grading more rigorous than appraisal institution standards

TASAKI standard

GIA
standard

External
appraisal
standard

TASAKI has set its own clarity grading system (appraisal standards) for diamonds that have already been graded by an external appraisal institution. In cases of diamonds that are on the borderline between two grades, we judge strictly at the lower grade. In doing so, we ensure that our grading standards remain reliable.

04 COLOUR

The closer a diamond is to colourless and totally transparent,
the greater is its rarity value

D

E

F

G

H

I

J

K

L

M

N

O

P

Q

R

S

T

U

V

W

X

Y

Z

Colourless

Near Colourless

Faint Yellow

Very Light Yellow

Light Yellow

Out of 23 colour rating grades,
TASAKI only accepts diamonds in the top five grades (H and higher).

In colour grading, appraisal is conducted by a diamond grader under an appropriate light source.
Colour is rated according to 23 grades from the highest grade of D (colourless and totally transparent) to Z, depending on the yellowness of the stone.
Only diamonds of grade H (close to colourless) or higher are accepted for the TASAKI BRIDAL range.

Using only diamonds
that have no fluorescence

Diamond with
fluorescent properties

TASAKI
DIAMOND

Some diamonds have strong fluorescent properties that make them glow when they absorb ultraviolet light. However, they appear cloudy under natural light, so TASAKI checks for fluorescence at the rough diamond stage, and uses only diamonds that have little or no fluorescence.