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This paper presents geology aspects of jeweler demantoid new manifestation, which was recently discovered in the Polar Urals. The mineralogical characteristics of the manifestation are described, demantoids chemical analysis results are shown, and comparative analysis of demantoids with samples from classical Ural deposits is given. The crystal chemical characteristics of demantoids from this manifestation are studied and color origin of these garnets is investigated. Demantoid mineralization is presented in two types: single rounded grains and granular discharges from 2 to 5 mm, which form small chains up to 1-2 cm; edges of the garnet. The garnet purity is low; there are numerous inclusions of tremolite, gas-liquid inclusions, hollow channels and cracks. Crystals are categorized as cleanliness 2. The presence of byssolite is the most characteristic sign for demantoids under study (the “horse tail” inclusion). The nature of byssolite distribution, morphology of its aggregates allows us to talk about several types: clustered secretions; needle inclusions; matted-fibrous aggregates. The Skalny manifestation is confined to the western endocontact of the ultra-massif Cyum-Keu massif and is represented by veins zone, in which there are numerous veins of jadeite, albite-jadeite and plagioclase-jadeite bodies. The host rocks for garnets are serpentized ultrabasic rocks. Aggregates are found in cracks (rupture) which filled by tremolite. Demantoids comparative analysis of the Skalny manifestation and famous Ural field the Novo-Karkodinskoe deposits (Middle Urals) with following comparison criteria were used: geology, deposit, structure of veins, morphology, gemological characteristics. Garnet mineralization was studied in the Skalny manifestation and garnet group mineralogical series was established: andradite, demantoid, topazolite and uvarovite. Together with garnet, talc, antigorite, tremolite and chromite are found. The noble varieties of andradite (topazolite, demantoid) can be used as a material for obtaining gemstones of average quality. [ABSTRACT FROM AUTHOR]

The paper considers a problem of gemstones valuation, based on real data. The main goal includes constructing a model that determines the evaluated price of a given stone on the basis of its description, expressed as a set of input variables values. A classic approach, utilising a multiple linear regression tool, is compared with nonlinear multilayer perceptrons. As the dataset contains a number of qualitative variables (e.g. gemstone colour purity, the clarity of the structure and a symbol of the certifying authority), the important part of solving the problem is selecting and implementing a proper method of encoding qualitative variables in a numeric form that is accepted by statistical and neural tools. The adoption of method for numerical representation of qualitative information is primarily determined by the scale of measurement for a given variable. In the research presented here, some classic encoding methods have been considered: for nominal variables - "one out of N", "equilateral coding", and representation based on a single numerical variable; for variables expressed on an ordinal scale, additionally selected variants of so called thermometric methods can be implemented. A number of experiments, with the use of Statistica software packet, have been made, and their results have been presented and discussed. Conclusions show generally higher effectiveness of neural networks over the multiple linear regression in the considered issue, but also significant indications concerning qualitative data preprocessing (encoding them in a numeric form) for valuation models have been introduced. [ABSTRACT FROM AUTHOR]

Gemstones inspired people since the very beginnings of humankind due to their esthetic nature and as a symbol of lasting value and social superiority. Precious and decorative stones from the East Kazakhstan Region are known in this area of Central Asia since the early prehistory. The most precious among the Kazakhstan gemstones - emeralds - were processed by the factories in the Urals in the 16th-19th Centuries. Among other well-known non-metallic minerals there are sapphires, topazes and tourmalines, mostly occurring in the NE part of the territory. Local agates and chalcedony are largely represented by hand-made articles. There are also varieties of high-quality quartz and many other kinds of decorative stones, including the famous Altai jasper. The traditional position of local gemstones has changed with their modern application in science and technology. On contrary, demands for the local natural stones and their use for jewelry and artistic goods/souvenirs has dropped sharply due to the increasing introduction of synthetic stones to the World markets and their mass-scale and cheap production. Yet, the traditionally most precious gemstones have been stable in the people's value ranking, also as a form of a financial investment. Comparing to other countries, the East Kazakhstan precious stone deposits are still poorly known and only locally exploited. The national industrial application of the Kazakhstan hardest minerals is multi-facetted. Diamonds are widely used for cutting and polishing of other hard materials; rubies and sapphires are largely synthetic and applied in high-precision medical and other technical instruments. Quartz from the Altai region is employed in high-tech implements in radioindustry, optics, etc. Finally, varieties of agates and chalcedonies are used in production of detail parts of electronic precision balances and other measurement tools. Yet, for a genuine art and jewelry, the precious stones still remain as the basic, irreplaceable and eternal material in which achievements of human inspiration are permanently retained. In spite of the immense mineral riches, the East Kazakhstan gemstones industry is still largely limited to small-scale and almost exclusively locally operating mining activities. The major natural potential of precious non-metallic minerals justifies new prospection activities for the gemstone-hosting mineral ore deposits that are currently carried out, promising a revival of the once flourishing Central Asian gemstone trade and economy. The paper provides a short overview of (semi-) precious and decorative non-metallic minerals of the East Kazakhstan provenance and their future exploration in terms of their predictive depositional ore distribution and industrial applications. [ABSTRACT FROM AUTHOR]

A large group of commercial minerals known as “industrial minerals” is used worldwide. Industrial minerals are understood as useful mineral deposits, i.e. all minerals extracted from the earth, except for energy raw materials, metals, water and gemstones, and used for industrial purposes owing to their physical, chemical and mechanical properties. The geological structure of the continental eastern Fennoscandian Shield (Karelian Region), the basement of the East European Platform, is controlled by its long geological evolution from 3.5 Ga to the present. The extraction and use of mineral resources in what is now Russian Karelia began in the Old Russian state founded in the 9th century, when large-scale mica production was launched followed by salt production in salt works on the White Sea shore. The late 18th century saw the production of Tivdian-Belogorsk and Ruskeala marbles, Olonets gabbrodiabase, Shoksha crimson quartzite and Serdobol granite in stone quarries. The first attempts to study shungite were made in the 19th century. Long-term studies of Karelia’s industrial minerals have shown that Karelia’s mineral potential comprises a variety of essential multi-purpose industrial minerals such as diamond, graphite, shungite, kyanite, garnet, fluorite, quartz, pegmatitic and magmatic feldspar, muscovite, talc, alkaline asbestos and others. Of great importance are Precambrian dimension stone and crushed stone used in civil engineering. It is important to update technological methods for optimum processing of priority industrial minerals such as graphite, kyanite, fluorite, high-purity quartz, soapstone and shungite rocks. Dimension stone and aggregate stone production has a good outlook for the future comparing Karelian resources with a similar one in Finland. [ABSTRACT FROM AUTHOR]