Colorimetry Study And Quality Evaluation On Labradorescence

The labradorite stone is one of the main rock forming mineral species,and its typical special optical effect(labradorescence)makes the surface of the feldspar show a changeable and beautiful color appearance,which is the main reason for its being as a member of gemstone mineral.The labradorensce of the labradorite shows that with the rotation of the incident angle of the light source,the color appearance of the gemstone surface will change dynamically,thus producing the iridescent visual effect.The labradorescence of different degree and quality level will directly affect the market price of the labradorite.And how to make scientific analysis and quality evaluation of the labradorescence of the feldspar,the academic circles have not made systematic theoretical guidance and scientific research on it.Although the academic circles still hold different views on the color origin of labradorites,the mechanism of the color formation caused by interference of the internal structure and the incident light on the surface(labradorescence)is basically acknowledged.In view of this,this dissertation will first carry out the research steps consistent with the previous scholars,and combine the experimental results of the instrument test to analyze and verify exactly what type of labradorite internal parallel structure interferes with the incident light,resulting in the labradorescence.Then,based on the results of the verification and analysis of the color genesis of the labradorite,this dissertation will further study the color of the labradorescence based on colorimetry.The color of the labradorescence will change with the incident angle of the light source,and the dynamic change of color appearance(labradorescence)occurs,and the core of the dynamic changing process is "change",so the "direction" and "degree" of the change are the key reference factors to evaluate the effect of the changing process.In view of this,this dissertation quantifies and studies the changes of color features(hue,saturation and lightness)of labradorescence by selecting the CIE1976L*a*b* uniform color stereo space system recommended by the International lighting Commission.First,the typical labradorite samples were sampled and divided into three major colors(blue,yellow and green)of three different main colors,and then the labradorescence samples in different color series were graded and evaluated,so as to establish a grading system for the labradorescence.Secondly,this dissertation will decompose and quantify the dynamic changing process of the labradorescence under different illumination angle of the light sources,combining the color classification results of the first step.By analyzing the data between the "color grade" and the incident angle of the light source,the "direction" of the color appearance’s change is studied,and the relationship between the color difference value of the color parameter and the incident angle data is discussed,and the result of the "degree" of the color change of its labradorescence is obtained.Combining the two points above,a scientific and reasonable quantitative analysis is made to the special optical effect of the labradorite(labradorescence),and the quality evaluation system of the labradorescence of the labradorescence is established.