GB/T 18781-2023Cultured pearl grading (English PDF)

Foreword

This document is in accordance with the provisions of GB/T 1.1-2020 "Guidelines for Standardization Work Part 1: Structure and Drafting Rules for Standardization Documents" drafting.

This document replaces GB/T 18781-2008 "Pearl Grading". Compared with GB/T 18781-2008, except for structural adjustments and editorial changes, in addition to the dynamics, the main technical changes are as follows:

--- Changed the scope (see Chapter 1, Chapter 1 of the 2008 edition);

---Changed natural pearls, pearls, seawater pearls, freshwater pearls, bead core, nacre, nacre thickness, color matching, iridescence, diameter difference, terms and definitions for Score, Blemish, Smoothness, Match, Pearl Master Sample, Pearl Trim, and Mixed Pearls (see Chapter 3, Chapter 3 of the 2008 edition);

--- Added the terms and definitions of nucleated pearls, non-nucleated pearls, nacre, nacre thickness ratio, and pearl grading (see Chapter 3);

--- Change "quality factors and grades of seawater pearls" and "quality factors and grades of freshwater pearls" to "quality factors and grades of pearls" Gender (see Chapter 4, Chapter 4 and Chapter 5 of the 2008 edition);

--- Changed the color (see 4.1, 4.1 and 5.1 of the 2008 version);

---Changed the expressions of shape level, gloss level, smoothness level, bead thickness level and matching level (see 4.3~4.6, 5.2.3.2, Chapter 4, Chapter 5 and 6.4.2.2 of the 2008 edition);

--- Increase the thickness level of non-nuclear pearl layer and the thickness level of nucleated pearl layer (see 4.6.1 and 4.6.2);

---Changed the minimum level requirements for the quality factor of jewelry-grade pearls (see 5.2.1, 6.2 of the 2008 edition);

---Changed the inspection methods for color, gloss, smoothness and bead thickness (see Chapter 6, Chapter 7 of the 2008 edition);

--- Increase the gloss level division rules (see 6.4.1);

--- Added the calculation method of bead thickness ratio (see 6.5.2);

--- Added quality inspection methods (see 6.8);

---Changed the basic content of the grading report or certificate (see 8.1, 9.1 of the 2008 edition);

---Deleted the expression method and identification of the quality factor level (see 9.2 and Chapter 10 of the 2008 edition);

--- Added the thickness level of nucleated pearl nacre produced by Pinctada martensii (see Appendix A).

1 Scope

This document specifies the quality factors and grades of cultured pearls (hereinafter referred to as "pearls"), pearl grades, requirements for grading personnel, grading reports or the basic content of the certificate and other requirements describe the inspection method.

This document is applicable to quality evaluation activities related to pearl production and trade.

This document does not apply to the grading of irradiated, dyed, etc. pearls and composite pearls.

The grading of natural pearls and pearl ornaments can be implemented by reference.

Note: Assembled pearls refer to pearls that are spliced together with other objects and give people an overall impression.

2 Normative references

The contents of the following documents constitute the essential provisions of this document through normative references in the text. Among them, dated references For documents, only the version corresponding to the date is applicable to this document; for undated reference documents, the latest version (including all amendments) is applicable to this document.

GB/T 16552 Names of Jewelry and Jade

GB/T 16553 Identification of Jewelry and Jade

GB/T 23886 Method for Determination of Pearl Pearl Layer Thickness Optical Coherence Tomography

3 Terms and Definitions

GB/T 16552, GB/T 16553, GB/T 23886 and the following terms and definitions apply to this document.