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Diamond Knowledge (4C)

CUT GRADE

CUT GRADE refers to a diamond’s proportions and the quality of its finish. A well-cut diamond (Excellent Grade) captures the light around it and makes that light perform in breathtaking ways. 

Cut Grade can be divided into FIVE grades : 

Excellent, Very Good, Good, Fair and Poor.



PROPORTION
PROPORTION refers to a polish diamond’s dimensions, facet angles and the relationships between them.

For standard rounded brilliant diamonds, reports the measurements of eight proportions. For fancy shape diamonds (those other than standards round brilliants), reports measured values for table size and total depth. For all diamonds, girdle thickness and culet size are reported with word descriptions based on visual assessments.

 

FINISH

FINISH refers to the quality of a diamond’s polish (the overall condition or smoothness of its surface).

 

POLISH

POLISH is visually assessed and graded in one of the following categories : 

Excellent, Very Good, Good, Fair and Poor.


SYMMETRY

SYMMETRY exactness of its outline, and the shape, placement, and aligment of its facets.

1. DEPTH

Its height measured from the culet to the table (57.5% - 63.0%)

2. TABLE

table is the largest facet of the stone, comprising the flat surface on the top. The table percentage is the ratio of the width of the diamond's top facet in relation to the width of the entire stone (52% - 62%)

3. GRIDLE

Forming the outer edge of the diamond, this is where the crown and the pavilion meet and is the widest part of a diamond. (THN to STK)

4. CROWN       ANGLE

the degree of the angle formed between the table and the girdle.(31.5°- 36.5°)

5. CROWN       HEIGHT

the height of the diamond from the girdle edge to the surface of the table facet. (12.5% - 17.0%)

6. PAVILION      ANGLE

pavilion angle is the angle of the pavilion facets in relationship to the girdle plane.(40.6% - 41.8%)

7. PAVILION      DEPTH

measured from the culet to the intersection of the pavilion main facet and the girdle

8. CULET

Culet size is described as the width of the culet facet. (NONE - SMALL)

9.STAR
   LENGHT

length of the star facet expressed as a percentage of the girdle-to-table distance. (45% - 65%)

10. LOWER        GIRDLE         /

      LOWER        HALVES

he length of a pair of lower-half facets expressed as a percentage of the girdle-to-culet distance. (70% - 85%)

Color

The color of every piece of diamond varies slightly, the different natural hues are classified into 23 grades starting from D to Z. The most rare and valuable is the “Colourless” grade D, E and F, the most common are “Near Colourless” grade G, H, I and J ; “Sightly Tinted” grade K, L and M;“Very Light Yellow” grade N, O, P, Q and R ; “Light Yellow” grade S, T, U, V, W, X, Y and Z; Grade Z+ are “Coloured Diamonds”. Diamonds also have some other variety of colours, for example : brown, orange, pink and blue etc.

Carat

A diamond’s weight is measured in carats. One carat is equal to 0.2 gram, and is divided into 100 points, so that a diamond of 0.50 carat is described as a diamond of 50 points.

Clarity

Every diamond contains natural “birthmarks” in the form of minute traces of other minerals arisen during the crystallization process. The more and larger the intrusions are, the greater the influence would be.

Fluorescence

Diamond with fluorescence, some may have phosphorescence. 

Fluorescence (FLUORESCENCE) indicator means when the diamond under the strong ultraviolet light blue or other colors of light. Fluorescence only has little effect on the value of diamonds. The fluorescence of diamonds being particularly strong, there is therefore a part of the diamond will affect its transparency. Sometimes, the fluorescent yellow line to improve the color of the diamond level, because of the blue and yellow near colorless, so the formal diamond grading certificate, in general, that a fluorescence level. 

 

FLUORESCENCE grading:

(1) NONE

(2) FAINT

(3) MEDIUM

(4) STRONG

(5) VERY STRONG 

 

The above information for reference only.