[in Japanese]

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The geological and geographical features of the ruby deposit discovered in 1979 near Mount Brady in the metamorphic Arunta Complex of Central Australia. An account of its subsequent utilisation as a gemstone. Chemical analysis of the host rock and a discussion of the possible modes of its genesis as a guide for further discoveries.

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Large and relatively unexplored, Canada has yet to produce significant quantities of facetable gemstones. Nephrite jade from British Columbia is the only gemstone produced in large amounts today. Ornamental minerals such as amethyst crystals, labradorite, sodalite, rose quartz, rhodonite, peristerite and amazonite are exploited on a limited scale. Ammolite, and interest-ing new fossil gem material, has recently appeared on the market. The hessonite variety of grossular and green apatite had limited commercial success. Other gemstones discussed are uncommon and/or occur at localities difficult to reach. They are as follows: diamond, corundum, beryl, quartz, grossular and almandine garnets, cordierite, vesuvianite, amber, oligoclase and lapis lazuli.

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[in Japanese]

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Since about two years gems are mined in the Tissamaharama area in Southern Province, Sri Lanka. Main places of interest are Amarawewa, about six miles from Tissamaharama in the direction of Kataragama and Kochipadana, about three miles to the east of Kataragama. Gems are found in alluvial deposits in pits with a depth of about one yard, a gem-bearing level situated at about that depth. Working may be considered, therefore, as surface mining, in particular in Kochipadana. In Amarawewa mainly gem-quality sapphire is found. Also big quantities of blue spinel and yellowish brown tourmaline occur. Apart from some moonstone and aquamarine, also rare gem-stones like almost colourless scapolite, greenish apatite, diopside and sphene are discovered in the material collected by the author in February 1981. In Kochipadana not only corundum, especially sapphire, occurs, but also beautiful yellowish brown tourmaline, blue spinel, almandine garnet and hessonite garnet are found in big quantities. Less important are zircon, beryl and quartz. Amongst the unusual gemstones apatite, diopside and a light green spodumene may be mentioned. It is striking that the gem mlinerals found in this area, are only slightly waterworn. Most of them are well-developed crystals, an observation indicating that their natural transport has been considerably less than that of gem minerals else-where in Sri Lanka. It is not unlikely therefore that further investigation will solve the problem where these gem minerals are formed originally, somewhere in the same part of the country.

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[in Japanese]

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Recent work by Thomas Gold and Steven Soter at Cornell University on the nature and quantity of gases deep within the earth provide new ideas on that most puzzling of gemmological problems: the origin of diamonds. Diamonds can be interpreted as having been formed by the movement of a dense gas, one of whose constituents was abiogenic methane, through pore spaces at depths of 150-250 km, depositing crystals of essentially pure carbon. The gas in question is held to have been an original constituent of our planet and its movement is interpreted as part of the continuing planetary outgassing process. Gas of identical origin can be called upon to account for the violent puncturing of the earth's crust by khmberlite diatremes and the safe ferrying of the rapidly cooled diamonds through a large vertical pressure/temperature region in which slow passage would doom the diamonds to reversion to ordinary carbon.

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This paper deals with some gemstones which have peculiar features which the author regarded new in comparison to literature and therefore reported them to the 18th International Gemmological Conference. They are : transparent brown Actinolite with rather high RI, emerald green Smaragdite, colourless Fe-free Andalusite and Fe-rich Andalusite as well as Fe and Mn containing Andalusite, called Viridine. Probably the first cut Bustamite and transparent Diaspore of sufficient size (up to 25 carats cut) from Turkey. Ekanite in emerald green colour. Emeralds from Zambia with very high Fe-contents and therefore RI up to 1.603. for the ordinary ray and all intermediate types down to 1.589, Emeralds with a distinct zonal growth and Zambian Emeralds show-ing a peculiar dichroism (green in one and blue in the other direction) and absorption spectra as mixtures of the spectra ofEmerald and Aquamarine. Lechleitner synthetic Emeralds (mainly coated beryls) with very high RIs due to a very high Cr-contents, and multiple refractive indices. Garnets mixtures of Spessartite and Pyrope. Vanadium-grossularites with high RI due to high V-contents as well as Grossularites with 10w RI due to the fact that they are mixtures between Grossularite and Hydrogros-sularite (RI as low as 1.700) and mixtures between Grossularite and Vesuvianite (mainly RI around 1.720). Gem Herderite and Kainmererite (a Cr-rich Chlorite). Transparent Mn-Clinozoisite is described and some gem Scapolites. Emerald green Kyanite from Tanzania, Gahnospinels, bicolour Spodumene, and colour change Garnets. The Rls variety of Taaffeite due to the Fe-contents and yellow Topazes from Schneckenstein/Saxonia with intermediate RIs. Tourmalines with RI as low as 1.605 and 1.619 as well as red Tourmalines with very high RI of 1.629 and 1.660 and also rough Tourmalines with multiple RI due to vicinal faces. The new mineral Schlo〓macherite is mentioned and blue green Zoisite.

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[in Japanese]

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ldentification of coloured quartz varieties and their discrimination from other minerals are not difficult for a gemmologist. However , quartz and its coloured varieties, being grown under condi-tions similar to natural crystallization environ-ment, create more problems than any other synthetic material. This is particulary true for synthetic amethysts, Fe-citrines and smoky , quartz whose structural and morphological properties and colour centres are virtually identical to those of natural crystals. To recognize synthetic quartz among faceted coloured stones a gemmologist should consider distribution of numerous inhomogeneities (growth pyramids and zones, twins, inclusions etc.) in the bulk of the crystal as well as all probable directions of cutting and various orientations of these directions in the process of faceting the stone in question. All coloured synthetic quartz material is known for the absence of chlorite, sericite, hematite, amphiboles, metal sulphides and other fluid inclusions common for natural crystals. Colour itself may be a determining factor in identification of green, brown and blue synthetic varieties. The most convincing sign for the synthetic nature of Fe-citrines is an absence of Dauphine and of polysynthetic Brazilian twins in synthetic crystals. It is relatively simple to identify synthetic amethyst stones made of crystals grown in nearly neutral fluoride solutions. They always display some "streamline" pattern (fiber structure) with orientation following crystal optical axis. Furthermore, they have no twins and their IR absorption spectra have characteristic band at 3640,3670 and 3685cm<-1>, common for all quartz grow, n in F-bearing media. These bands have never been observed in natural quartz, nor in the crystals synthesized in alkaline solutions. Amethyst synthesized in alkaline solutions is hardly distinguishable from natural amethyst. It is especially true when ston'es are in high grade with homogenous colour distribution and with-out twins. If stones are too homogeneous and contain no twins, those who are familiar with amethyst will be suspicious of the origin. The ex-istence of Da, uphi6 and Brazilian twins may offer proofs, though not conclusive, of natural origin, and simplify identification of amethysts.

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Coating of diamonds has recently been widely in practice to improve the colour grade. This has aroused severe problems to gem market. This paper reports an easy technique to identify such stones. Since the film material coating diamond brilliants is softer than diamond, tiny and thin scratches are easily formed on their surface, which are not detectable with naked eyes or even with an ordinary microscopes. If such scratches could be detected by some means, the coated stones are easily identified. Interference contrast microscopes can detect steps with height down to a few Angstrom. We have applied the microscope of this type to commercially circulated coated stones, as well as stones to which Ti0_2 film is experimentally produced. We found, these stones can be easily detected under the microscope of this type by the presence of scratches and heterogeneities in coating. We also scratch artificially a coated stone by polishing powder with lower hardness than diamond, which also produced observable scratches under the microscope.

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Raman spectrometry shows that colour of natural corals is the consequence of the contain of carotenoid; in addition, differences in fiuorescence permit to distinguish natural corals from dyed corals.

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