The samples were inspected, identified and classified according to GB/T 16552 Name of Jewelry and Jade and GB/T 16553 Identification of Jewelry and Jade.
According to the different growth modes, it can be divided into natural seawater pearls and natural freshwater pearls.
According to different growing waters, it can be divided into marine cultured pearls and freshwater cultured pearls.
According to the presence or absence of nucellus, it can be divided into nucleated cultured pearls and seedless cultured pearls.
According to whether shells are attached or not, they can be divided into free cultured pearls and attached cultured pearls.
Pearls can be divided into natural pearls and cultured pearls according to the production mechanism, and can also be divided into seawater and fresh water according to the production waters. According to the national standard GB/T 16552-2003, cultured pearls can be abbreviated as pearls, but the English name is still cultured pearl.
Step 2: Quality factor level evaluation
Quality factors such as color, size, shape, luster, smoothness and bead thickness (nucleated pearls) were evaluated.
1. color
The colors of pearls are divided into five series: white, red, yellow, black and others, and each series includes a variety of body colors. For example:
White series: pure white, milky white, silvery white, porcelain white and so on.
Red series: pink, light rose, lavender, etc.
Yellow series: light yellow, beige, golden yellow, orange yellow, etc.
Black series: black, blue-black, gray-black, brown-black, purple-black, brown-black, iron-gray, etc.
Others: purple, brown, cyan, blue, brown, fuchsia, green, yellow, light blue, green, bronze, etc.
Pearls may have associated colors, such as white, pink, rose, silvery white or green.
Pearl may have halo, which can be divided into strong halo, obvious halo and general halo.
Color description: body color description is the main one, accompanied color and halo color description are the auxiliary ones.
2. Size
Round, round and nearly round pearls are represented by the minimum diameter, cultured pearls with other shapes are represented by the maximum size multiplied by the minimum size, and loose pearls can be represented by the pore size range of pearl sieve.
Measure the size of the pearl (according to the calculation, it can be concluded that the roundness of the pearl is a perfect circle, a circle or a near circle).
3. Shape level
4. Gloss grade
5. smoothness
Compared with the standard sample, the following defects may appear:
6. Weld thickness grade
At present, the detection methods include X-ray photography, OCT optical coherence chromatography and direct measurement.
Step 3: Determine the grade of pearls.
According to the quality factors of pearls, pearls used for decoration are divided into two grades: jewelry-grade pearls and handicraft-grade pearls.
1. Minimum requirements for quality factors of gem-grade pearls
Gloss grade: medium (c).
Smoothness: pearls with the minimum size above 9mm (including 9mm): defect (D).
Pearls with the smallest size below 9mm: small defects (C).
Thickness of nacre (nucleated pearl): thin (D)
2. Craft pearls
Those pearls that fail to meet the requirements of jewelry-grade pearls are craft-grade pearls.
Step 4: Grading pearls in multi-pearl ornaments.
Includes the determination of the overall quality factor level and the determination of the matching level.
A, determining the single quality factor level of each pearl in an ornament;
B, respectively counting the percentage of pearls of the same grade in each single quality factor;
C. When the percentage of a certain quality factor higher than a certain level is not less than 90%, the level is designated as the overall quality factor level;
D. Determination of mating grade: (see the table below)
Step 5: Pearl grading results are expressed.
1. English code of each quality factor grade of pearl grading results.
The grading results of pearls should be expressed in the order of shape, luster, smoothness, nacre thickness (if involved) and compatibility (if involved).
For example, the quality factor level of seawater pearl necklace is expressed in Chinese as:
Shape level: circle A2
Gloss: extremely strong a.
Finishing grade: flawless a.
Pearl thickness grade: medium C.
Mating level: very good A.
The English code of quality factor level is continuously expressed as A2AACA.
2. The clear contents of the grading mark of pearls shall at least include:
(1) Name (seawater pearl or freshwater pearl shall be marked);
(2) Pearl class;
(3) size;
(4) Shape, luster, smoothness, bead thickness (if involved) and compatibility (if involved);
(5) the name and address of the manufacturer;
(6) Implement standard numbering.
Classification and certification of NGTC pearls.
The National Jewelry and Jade Quality Supervision and Inspection Center has opened the grading inspection service for original pearls and decorative pearls, and issued the certificate of pearl grading (see photo). The certificate provides information such as the types of pearls, the grades of the six quality factors of pearl grading, and the pearl grades, which will make consumers have a clear understanding of all aspects of the quality grade information of the purchased pearls, and make consumers feel at ease after buying them.