The Feldspar In Feicui From Myanmar And The Influence On The Quality Of Feicui

Myanmar, out of many places producing feicui in the world, is the only one that can produce feicui achieving the level of gem and having been extensive mining and processing. Myanmar feicui, as a kind of jade, contains a variety of minerals. Feicui compose mainly by pure jadeite. In recent years, people tend to allocate a few jade composed by omphacite or ureyite under the scope of feicui. However, there are some arguments towards this classification within the industry. In addition to the principle pyroxene mineral, the secondary minerals of feicui are amphibole and feldspar. The major feldspar mineral in feicui is albite. As a common secondary mineral, feldspar minerals, especially albite, have shared a close relationship with jadeite minerals. Therefore, in order to make clear about the formation of feicui deposits and the evaluation of original feicui stone, it is highly worthwhile to have a close study on the relations between albite and jadeite minerals.Through samples of conventional gemological testing, IR tests, XRD testing as well as electron microprobe analysis, the feicui did contain a certain amount of feldspar minerals. By calculating the chemical formula of the mineral feldspar crystals, we have found that this mineral is albite. Furthermore, by using the data result of XRD, we are able to make out the calculating formula of the forming condition of long-ramp stone, thus getting the conclusion that this mineral should be cold albite.Using the thin slice observation under the polarized microscopy, we have found that there are two existential ways for albite minerals in emerald: one is the first generation of albite which is earlier than jadeite or grows together with jadeite minerals; the other is albite of vein type which is formed by the hydrothermal fluid effect. By comparing the existing situation of albite in different grades of feicui, we have discovered that the first generation albites mainly appear in the low-level emerald. By synthesizing the influence of the two albite's occurrence towards feicui's structure, transparency, color and many other factors, we can reasonably get the conclusion that the existence of albite will reduce the quality of feicui. This conclusion will take on certain significance to the evaluation of original feicui stone.