gems, jade, nephrite, Taiwan, nephrite cat’s eye

Two samples of Taiwan's jade, one of them with a clear cat's-eye effect, have been studied by optical, x-ray, thermal and electron microprobe analyses and SEM investigations. They showed that both samples are tremolitic members of the tremolite-actinolite- ferroactinolite series, with identical chemical and mineralogical composition. The diverse shades of green colour and cat's-eye effect are related to different arrangements of the fibres.

gems, jade, nephrite, Taiwan, amphibole jade, jade cat’s eye, tremolite cat’s eye

The Taiwan Cat's-Eye"is a tremolite cat's-eye. The gem material, cat's-eye tremolite occurs as veins at the contacts of graphite-sericite schist and serpentinite sills in association with nephrite, asbestus, talc and diopside-dominant skarn in the Fengtien area, south of Hualien. It is greenish yellow, pale yellow, honey yellow, green, rarely dark green, dark brown or black in color; translucent to opaque. H. 6-7, G. 3.045. Under the microscope, cat's-eye tremolite is colorless or pale green in color, consisting solely of fine, long sub-parallel fibers of tremolite in contrast to nephrite. Twisting or bending and wavy extinction are common. c∧Z' 0゜-10゜. α 1.613, β 1.626, γ 1.637; γ-α 0.24. The X-ray data are very similar to those of tremolite from St. Gotthard, Switzerland. Four chemical analyses reveal no marked differences in composition between the varieties of different colors, showing about 10% of the ferro-actinolite molecule. Some gemological features are also given. Diopside shows more crystal forms than previously reported, and the occurrence of grossularite is limited to diopside-grossularite veins near the contacts. Minor uvarovite and vesuvianite were first found in Taiwan. The former occuring as minute inclusions in diopside has n l. 778 and a_0 11.87A, corresponding to uvarovite with 10% Cr_2O_3. The latter of small prismatic crystals shows similarity in X-ray data to vesuvianite from Canzoccoli, Italy. The mineralization of the Fengtien nephrite-asbestus deposits may be divided into two stages : skarn formation and ore deposition, which might have taken place during serpentinitization by hydrothermal solutions rich in silica and lime. Cat's-eye tremolite was formed evidently later than nephrite."

gems, euclase

corundum, synthetic corundum.7, Verneuil, Czochralski, pulling, flux, hydrothermal, gems

gems, ancient mining, Europe, archaeology, archaeogemology

Our knowledge of the organization and life of the Roman mines in the Danubian provinces is strikingly incomplete considering the importance of the subject. Fresh finds and research, however, make the picture somewhat clearer; the following discussion concentrates on several points which, studied primarily on the basis of written sources, allow of a certain progress. The main conclusion of the present study is that Roman mining in the Danubian provinces—and, no doubt, also elsewhere—was more of a system than is commonly thought. That branch of industry demanded special care which exceeded the means of an area or a province, as illustrated by the transportations of peregrini from Dalmatia to Moesia Superior and Dacia for compulsory work in the mines. The hard fact that metals, especially precious ones, were both rare and needed, naturally led to the relative centralization of the mining administration, and to a distinction between the provinces which were rich in minerals and those which were not. Conceivably, such a state of affairs must have had manifold consequences. One of them should be stressed: the gradual municipalization of the provincial territory, which is a process common to all the Empire, was bound to affect the countries of central Noricum, southern Pannonia, northern Dalmatia, and almost the whole of Moesia Superior in a far lower degree, owing to the occurrence of mines within the vast fiscal domains. This had a bearing on all aspects of life there, notably on the organization of the portorium and on the degree of Romanization of the indigenous population.

gems, history of gemology, history of mineralogy, Arabic mineralogy, history of science, Greek science, astronomy

Through the increased use of Carbon-14 dating in West African archaeology, it is now widely accepted that iron was known to the ancient Nok peoples of present-day Ghana and Nigeria during the pre-Christian era. The Nok Culture" was first identified in 1959 by Bernard Fagg following excavations at the Nok Site in central Nigeria, and stratigraphic analysis placed the culture in the centuries surrounding the birth of Christ. Iron was discovered at the site, and Fagg’s announcement of its unexpectedly early use in West Africa came as a revelation to prehistorians. Before this discovery, the prevailing view was that iron had been introduced relatively late, either through Islamic influence or contact with the Portuguese after 1400. However, subsequent fieldwork revealed furnace remains alongside Nok artifacts, confirming that iron was being smelted locally more than 1,500 years before Portuguese arrival. Remarkably, iron and slag appeared suddenly amid Stone Age remains, unlike the gradual technological progression seen in the Near East. This discontinuity suggests that iron technology was not an indigenous invention in West Africa but rather a product of external influence, likely diffused from the Fertile Crescent. The precise route by which iron-making knowledge reached West Africa, however, remains a subject of ongoing scholarly debate."

beryl, emerald, gems

Studies on the refractive indices and specific gravities of natural and synthetic beryls are reviewed. Effects of impurities, temperature and pressure on these propertles are discussed. For synthetic beryls, refractive indices and specific gravity are strongly affected by the water pressure applied during synthesis. The emerald with refractive indices as high as natural emeralds can be synthesized by using the high pressure technique.

gems

corundum, synthetic corundum.7, Chatham, flux, gems

gems, history of gemology, history of mineralogy, Arabic mineralogy, history of science, crystallography

Recent scholarship has greatly extended our understanding of the history of theories concerning the ultimate nature and structure of matter. This is particularly true for the period preceding the emergence of Dalton’s atomic theory. We now know something of the hierarchical theories of material structure prevalent in the seventeenth century, in the thought of Robert Boyle and Isaac Newton, for example. We have begun to perceive how important Newton’s ideas concerning the structure of matter and the forces that bound substances together or pulled them apart were for the physical and chemical philosophers of the eighteenth century. Dalton’s chemical atomic theory no longer appears quite so lacking in background as it did twenty-five years ago. At the same time, Dalton’s true innovation in turning from consideration of force to consideration of atomic weight has likewise been clarified.