Influence of Soaking of Unearthed Tremolite Jade Artifact on Jade Composition Identification

Soak-induced colour is not only an important apparent feature of unearthed jade artifacts, but also considered to be a valuable "beauty". So usually, imitated soak-induced colour has been seen in imitated ancient jade artifacts. The soak-induced colour can influence the gemmological characteristics of the jade and identification of jade composition. Based on the research conducted on unearthed jade artifacts from four different archeological sites, this paper presents a results of the influence of soaking on ancient jade artifacts, especially on luster, colour, transparency, porosity, density, hardness, composition etc. Such that useful information on how to identify the components of ancient jade accurately and how to discriminate fake soak-induced colour on imitated jade artifacts can be elucidated. In conclusion, Soaking influences the colour of unearthed jade. The more serious damage is caused by soaking, the more colour change is visible-usually darker. Soaking influences luster and transparency. The more serious damage is caused by soaking, the worse the luster and transparency become. With the degree of soaking change from mild to severe, luster changes generally from glassy luster to sub-glass luster then to greasy luster, wax luster and finally soil luster. Changes in the general transparency is from transparent to sub-transparent to translucent, and finally opaque. Soaking influences the density, porosity and hardness of the unearthed jade accordance. The more serious damage is caused by soaking, the higher the porosity is, thus it reduces the density and hardness. For example, the hardness of seriously soaked tremolite jade may become less than 5.5 (ranging from 4 up to 6). Soaking also influences jade composition. The main mineral components generally do not change and jade species does not change as well, but some parts may change in the type and concentrations of chemical elements.