1999  Vol. 1  No. 4

Abstract:
Among various types of Myanmar jades, the most important are the jades mainly consisting of clinopyroxene minerals. Those jades include jadeite-jade, omphacite-jade and kosmochlor-jade. Now, different views on whether omphacite jade and kosmochlor-jade should belong to jadeite-jade are held out. The paper mainly discusses the non-des tructive identification methods to separate jadeite-jade from omphacite-jade and kosmochlor-jade. The experimental results show that the quantitative analysis of chemical composition by EDXRF combining the reflectance FTIR can determine jade with relative: simplicity and homogeneity in mineralogical composition effectively. On theory, according to the data of EDXRF and the spectra of FTIR, the relations between EDXRF and FTIR in two series of jadeite-astridite-kosmochlor and jadeite-omphacitic jadeite-omphacite are discussed.
Abstract:
The colour grade of the colourless synthetic diamond produced recently by the American Chatham Company is close to F. The highest clarity reaches Grade SI1. The crystal is in the combination form mainly consisting of such simple forms as {111},{100} and {211}. The {110} simple form often does not grow perfectly. The lamellas growth veins is diagnostic on the corresponding crystal face. The absorption spectrum shows that nearly no impure nitrogen atoms are present in the crystal lattice of this kind of synthetic diamond. However, a few boron atoms (2802 cm-1) still present in the crystal lattice. Therefore, this variety of synthetic diamond belongs to a mixed variety of Ⅱa~Ⅱb types. At the room temperature, the characteristic absorption peak only occurs at 271 nm in the ultraviolet with the ultraviolet absorption limited within 235 nm. Stimulated by cathode ray, this synthetic diamond produces strong blue-white fluorescence and displays its specific cathodoluminescent geometric patterns, growth subdivisions and mosaic structure. The blue cathodoluminescent peak is located at 432.5 nm, with some individual sample associated with weak luminescence at 575 nm. The alloy inclusions associated with the composition of the contact agent are in different shapes. The EPMA-EDS energy spectral analysis shows that the chemical composition of the alloy inclusions consists primarily of Fe (65 %~72 %), and secondarily of Cu(10 %~12 %), and also a litlle of such elements as S and Si. Therefore, an approach to the identification of Chatham synthetic colourless diamond is presented under the normal testing condition.
Abstract:
Blue chalcedony is one of the most precious gemstones in Taiwan. The most popular imitations of blue chalcedony in Taiwan market are dyed chalcedony, dyed quartzite and blue opal. Recently we checked one of the new imitations and found its RI and SG very close to blue chalcedony but the spectrum of FTIR the same as glass. With the analysis of EDXRF we make sure it is a man-made glass.
Abstract:
Kosmochlor-jade and related amphibole-jade (rock) in Longken, Myanmar are studied. Their types, texture, mineral chemistry, X-ray powder diffraction spectrum,chemical composition and REE of whole rocks, etc, are elucidated. The protoliths of kosmochlor-jade and related amphibole-jade (rock) in Longken, Myanmar are considered as peridotites, chromite-bearing peridotites, or chromite bodies, respectively. At high or ultrahigh pressure, those protoliths reacted with SiO2, Na2O and Al2O3 melt through a series of metamorphism. Chromite was replaced mainly by kosmochlor, astridite or chromium-bearing jadeite, while peridot was replaced by chromite. As a result, there might be a contin-uous variation from amphibole-jade (rock) to kosmochlor-jade.
Abstract:
To study crystal chemical compositions ,mineral com binations, microfabric and vibrational spectrum of Hte Long Sein Jade from Myanmar, the EPMA,LRM and petrographic analytical testing techologies are employed in the research. The research indicates that Hte Long Sein Jade mainly consists of chromium rich jadeite, which occurs as mineral aggregate (> 75%). The crystal chemical formula of chromium-rich jadeite shows as (Na0.830Ca0.1440.974(Al0.782Mg0.156Fe0.025Cr0.0531.016〔Si1.992O6〕. The typical paragenetic mineral com binations are chromium-rich jadeite +astridite+jadeite+kosmochlor+ chromite. The internal feature of this jade is characterized by the stress deformational fibric. The LRS spectrum and the formative mechanism of Hte Long Sein Jade are discussed. The results show that Hte Long Sein Jade is similar to jadeite jade in crystal chemical compositions and vibrational spectrum, and can be called jadeite jade.
Abstract:
Shoushan Stone is a famous gemstone in Fujian and has more than 100 varieties. Over 50 samples of Shoushan Stone have been studied using XRD and IR. Shoushan Stone can be divided into three groups based upon the density. The first group has density of 2.57~2.67 g/cm3, consisting mainly of dickite; The second has density of 2. 71~2. 79 g/cm3, containing illite; The third has density of 2.81~2.87 g/cm3, with pyrophyllite as its major mineral. Therefore, it is possible to determine their mineral constituent on basis of their densities. There are differences in the mineral constituent between the varieties of Shoushan Stone. Gaoshan Stone, Duchengkeng Stone and Kengtou Stone are composed of dickite, Yuewei Stone and Furong Stone consist of pyrophyllite. Shanbodong and Qijiang Stones contain kaolinite. Tianhuang Stone, the best variety among Shoushan Stone, is complex in their mineral constituent, and dickite, nacrite or illite have been found as the major mineral. Most of samples of Tianhuang Stone have ilite as a minor mineral, which seems to be an important feature of Tianhuang Stone and is probably related to hydration during its formation.
Abstract:
In the recent years, a series of competitions of gem design and cut have been held. It makes progress in the design and cut technology. As a result,jewellery industry has been in a new stage. View on the point of aesthetics, the paper discusses the sculpt modality principles of gem design and analyzes some kinds of gem style.
Abstract:
Valuation approaches in jewelry appraisal are discussed in the paper. The purposes and types of appraisal, as well as valuation level are presented. The most important valuation approaches, the costing approach and market comparison approach, are analyzed in detail. The main contents and cautions in each step from acceptation of item,description and identification, gemstone grading, calculating jewelry cost, taxes and markups, to presenting the appraisal report, are systematically summarized.