Uranium Mineralization of Fossil Wood

Uraniferous sandstone deposits commonly resulted when uranium in groundwater precipitated in reducing environments caused by degradation of ancient wood and organic debris. However, the mineralogy of uranium in fossil wood has received relatively little study. Previous microscopic observations of petrified wood from a few uranium mines have demonstrated that uranium in fossil wood primarily involves the oxide mineral uraninite or the silicate mineral coffinite, often in association with metal sulfides such as chalcopyrite. These observations are applicable to primary ore zones that are located below the water table, where oxidation is inhibited. New analyses utilizing scanning electron microscopy and X-ray fluorescence (SEM/EDS) reveal that fossil wood from oxidized ore zones may contain a diverse variety of uranium minerals, including carnotite, tyuyamunite, and zippeite, as well as various vanadate and sulfate minerals. Uranium-bearing common opalized wood and stratiform common opal from two prospects in Nevada, USA, contain no identifiable uranium minerals. Instead, the element is dispersed in trace amounts within the opal.

Development of Glass-Ceramics from Soda Lime Silica Glass Waste by Direct Sintering Method for Opal Imitation

Natural opal, an amorphous, hydrous form of silica (SiO2-n-H2O), has been one of the favored precious gemstones for many centuries. Though beautiful, opal is very fragile and is damaged quite easily. Thus, opals of all varieties have been synthesized experimentally and commercially. The objective of this project was to synthesize and to compare crystalline opals. In this work, the development of powder sintered glass ceramics process based on soda lime silica glass waste with metal oxide powder enable jewelry applications. The substantial viscous flow of the glass led to dense products for rapid treatments at relatively low temperatures (900–1,000°C), whereas glass/metal powder interactions resulted in the formation of color agent crystals, provide enhancing optical properties. Several techniques were applied for characterization of the ingots. The chemical analysis was performed by Energy Dispersive X-ray Fluorescence (ED-XRF). The mineralogical compositions of the samples were determined by X-ray diffraction analysis. Raman spectroscopy was applied for optical characterization. The results were compared with a natural common opal. The present investigation demonstrated that the common opal with both color and colorless appearance can be synthesized by the technique, as the crystalline phase of opal structure was identified by XRD measurement. There is a great potential for such materials with novel functionalities for artificial gemstone application, i.e. opal forming.

Gemstone deposits of Serbia

Gemstone minerals in Serbia have never been regarded as an interesting and significant resource. Nevertheless, more than 150 deposits and occurrences have been recorded and some of them preliminarily explored in the last 50 years. The majority of deposits and occurrences are located within the Serbo-Macedonian metallogenic province and the most significant metallogenic units at the existing level of knowledge are the Fruska Gora ore district, Cer ore district, Sumadija metallogenic zone, Kopaonik metallogenic zone and Lece-Halkidiki metallogenic zone. The most important genetic type of deposits is hydrothermal, particularly in case of serpentinite/peridotite as host/parent rock. Placer deposits are also economically important. The dominant gemstones are silica minerals: chalcedony (Chrysoprase, carnelian, bluish chalcedony etc.), jasper (picture, landscape, red etc.), common opal (dendritic, green, milky white etc.), silica masses (undivided), and quartz (rock crystal, amethyst etc.). Beside silica minerals significant gemstones in Serbia include also beryl (aquamarine), garnet (almandine and pyrope), tourmaline, fluorite, rhodochrosite, carbonate-silica breccia, carbonate-silica onyx, silicified wood, howlite, serpentinite, marble onyx, and kyanite. This paper aims to present an overview of Serbian gemstone deposits and occurrences and their position based on a simplified gemstone metallogenic map of Serbia, as well as genetic-industrial classification of gemstone deposits and gemstone varieties.