Interpretation of National Standard Turquoise Grading

The standard of Turquoise Grading is based on the collection of big data. Analysis of total 51 955 turquoise samples has been finished, and turquoise samples have been classified according to colour (hue, saturation, brightness) and surface characteristics. This papers interpret the standard of Turquoise Grading in three aspects: The standard developing process, grading requirements and grading contents. Turquoise Grading is completed by naked-eye observation. The grading content includes colour, texture, surface cleanliness, luster, transparency and special patterns. HSB colour grading system is used for colour grading to standardize the classification of hue, brightness, saturation and uneven colour. Density test is used for texture grading. The grading standard has passed through the collection of opinions of the industry as well as the laboratory trial. It proves that the process of turquoise grading is easy to operate.