quality standard
4C of diamond

" 4C " was established by Gemological Institute of America (GIA) and is an international standard for evaluating the quality of cut jewelery diamonds. It is about. color / color (hue), clarity / clarity (inclusions), carat / carat (weight), cut / cut It is evaluated from the four points of (brilliance), and is abbreviated as "4C" from each acronym. This 4C is described in the diamond "certificate".
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Carat (weight)


carat is the unit of weight , and 1 carat is 0.2g . "Carat" is derived from the seeds of "carob (locust beans)". Carob seeds are so uniform in weight that they are used as weights in gemstones and are now used worldwide as the weight unit for gemstones.

Color (hue)


Color grade is an evaluation of slight differences in yellow tones. The GIA standard classifies stones into D (colorless) to Z (light yellow or light brown) based on the master stone. Completely colorless diamonds are extremely rare, but Houjudo has a wide selection of beautiful diamonds, mainly D-colored diamonds.


This shows the color tone and intensity of the fluorescence of how it reacts when a diamond is exposed to long-wave ultraviolet rays. In most cases, it has nothing to do with the beauty of the appearance, but its characteristics are described in the certificate as one of the means of distinguishing gemstones.

Cut (brilliance)


Cut is an important grade for light transmission and sparkle. Cut grades are evaluated on standard round brilliant diamonds with colors ranging from D to Z. In addition to diamond proportions (dimensions and facet angles), it is graded into 5 levels from Excellent (excellent) to Poor (poor) based on the polishing condition and contrast. ..


4c fancycut dia

"Cut" is different from "Cut" which is one of the evaluation criteria of 4C, and "Cut" may be used to express the shape of each diamond. The most common are standard round brilliant cuts, but all but the shapes mentioned above are called "fancy cuts".

Clarity (inclusions)


Polished diamond is magnified 10 times by and inspected, and presence / absence / position / size / property / number is comprehensively judged. Evaluate. Houjudo also has a large selection of rare FL (Flores).


The most reliable
diamond with GIA appraisal in the world

The diamond appraisal report is based on the above 4C, but the evaluation may vary slightly depending on the appraiser who actually appraises.
Houjudo recommends diamonds with a certificate issued by GIA, which is the most reliable in the world and has set the world standard. Cartier, Harry Whiston and many other global brands use GIA-certified diamonds, and in terms of security, GIA-certified diamonds with the GIA mark and appraisal number are better. I am relieved.