The Study On The Secondary Color Of Jadeite

Jadeite is mainly yielded in Burma and it has many colors. Its color can be divided into tow types on the cause of formation. One type is original color, the other is secondary color. The secondary color is often yellow and red. According to Electron probe analysis, the secondary color is formed because of the iron compounds in the cranny and clearance of jadeite. The distribution of secondary color in jadeite materials has one stated rule in which yellow is outer, the original color is inner, and red is between them. The outer mineral texture of jadeite materials is nearly same to inner's and the granularity of mineral becomes smaller from from inside to outside.By infrared spectrum study, the limonite (FeOOH nH2O) can be considered the main colorating mineral in the yellow and red jadeite, and the hematite is another colorating mineral in the red jadeite. The difference of color tone is due to the n value in the molecular formula FeOOH nH2O and the content of crystal water and adsorbent water. The iron ion came from the effloresced and eroded rocks, and formed Fe(OH)3 colloid reacted with the surface water. The colloid adhered the surface of jadeite, formed limonite after dehydrating and crystal. Then the secondary color came into being owing to the limonite subsidence. The iron ion which are needed for the secondary color mainly came from outside.The natural red jadeites can be easily identified from dying and heat-treated ones by infrared spectrum. The natural ones contain water which represents absorbing apices on the area of 1500-1700 cm-1 and 3000-3700 cm-1, while dying ones and heat-treated ones are not.