Comparing Study On Natural Coloration And Artifical Coloration Tremolite Nephrite Jade

Natural colored antique tremolite nephrite jades are much more valuable than artifical colored ones, so it is significant for identification of antique tremolite nephrite jade to distinguish whether its color is natural or artificial. It is helpful for the technology improvement of antique tremolite nephrite jade identification to study the genesis of its natural color and artificial color. However, such studies are few. Based on the comparative study on colored parts and fresh parts of natural and artificial yellow colored and black colored tremolite nephrite jades, their coloration genesis was researched. Methods of artificial antique identification were produced on the based of comparative study on coloration geneses of natural colored tremolite nephrite jade and artificial colored tremolite nephrite jade.Microscopic observation and analyses of gemological characteristics, XRD, chemical composition and infrared spectrum were adopted to study geneses of natural colored tremolite nephrite jade and artificial colored tremolite nephrite jade. The study shows 1) what causes yellow color of natural colored tremolite nephrite jade is the oxidation of ferric ions from bivalence to trivalence and also physical impregnation of trivalence ferric ions ; 2) what causes black color of natural colored tremolite nephrite jade is physical impregnation of manganese material; 3) the ferric and manganese materials in natural colored samples are amorphous; 4) the yellow color artificial sample might be dyed by organic dyestuff and the black color of artifcal colored sample might be caused by potassium permanganate; 5) all dyeing materials in artificial colored sample are amorphous; 6) the natural coloration makes tremolite nephrite jade change its color greatly and there is a transition layer where the colored part charges in to fresh part gradually on tremolite nephrite jade; 7) the artificial coloration also makes tremolite nephrite jade change its color greatly, but there is no such layer, and the colored part is very thin like something being painted;8) both natural colored and artificial colored samples decrease their luster and transparent; 9) the density of natural colored sample decreases; 10) the hardness degree and toughness of both natural colored and artificial colored sample decreases.