There are all kinds of diamonds in the jewelry market, including pure natural diamonds and irradiated and filled diamonds. There are white diamonds (actually colorless with white characters on a white background), yellow diamonds, and red, green, blue and orange colored diamond. From the shape, there are standard round diamonds, as well as heart-shaped, oval and pear-shaped diamonds. The most common diamonds in the market are white (colorless) standard round diamonds, so in the "4C" standard, the classification of diamond color, clarity and carat weight only refers to the classification of natural white (colorless) to light yellow (brown, gray) series polished diamonds with carat weight greater than 0.2, while the cutting classification only refers to standard round diamonds or white (colorless) to light yellow (. The "4C" standard is not applicable to the classification of colored diamonds, irradiated diamonds and filled diamonds.
In the "4C" standard, the color of diamonds is divided into 12 grades. The grading method is: the pure colorless diamond is defined as the highest color pole-extremely white, 100 color, which can be expressed by D or written as D( 100). With the increase of the yellow component of diamonds, the color grades gradually decreased to E(99), F(98), G(97) and H(96). In the diamond appraisal certificate, the color grade is usually expressed only by English letters. When the color grade is lower than n, it is generally considered that the diamond is no longer suitable for cooperative jewelry. The color grading of diamonds is determined by professional technicians who compare the diamonds to be graded with standard colorimetric stones repeatedly in the grading environment of specified standards. Or use a colorimeter to scan the diamonds to be classified in the visible range, and then determine them through a series of technical analysis and processing; The purity of a diamond is its purity. The higher the purity of a diamond, the less impurities, defects or flaws there are, and vice versa. Objectively speaking, flawless diamonds are rare. According to the standard, carefully observe the internal and surface defects of the diamond to be graded with a magnifying glass of 10 times. Under this condition, the clarity of diamonds can be divided into five grades: flawless LC, extremely defective VVS, slightly defective VS, defective SI and severely defective P, and further subdivided into sub-grades 10, namely LC, VVS 1, VVS2, SI 1, SI2 and P. Diamond cutting refers to the proportion and decoration degree of cut diamonds, which is an index directly influenced by human factors in 4C standard. The brilliance of diamond is attributed to its unique high refractive index and high dispersion (commonly known as "fire color"). Only excellent and proportional cutting can make all the incident light reflect, so as to show the unique luster, luster and flash of diamonds to the maximum extent. If the cutting is rough and disproportionate, it will cause "light leakage". Even if a diamond has good color and clarity, it can't have good light and its value. The simple way for consumers to judge the cutting quality is to pick up the diamond and stare at the shining light on the top of the diamond. If there are not many colors, the cutting is not ideal. According to the standard, cutting is divided into three grades: very good, good and average; The unit of mass (commonly known as weight) of diamonds is grams, but "carat" is still used as the unit of mass (weight) of diamonds in international diamond trade. 1 carat = 200mg = 0.2g. 1 carat is divided into 100 parts, and each part is called10.8. When the color pole, clarity and cutting conditions are similar, with the increase of diamond weight, its value increases geometrically. Consumers should choose diamonds of suitable size according to their hobbies and actual conditions.