corundum, properties.3, gems

corundum, synthetic corundum.7, flux, Verneuil, gems

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

Gunawardene examines the gemological characteristics of Chatham flux-grown synthetic blue and orange sapphires, emphasizing the increasing difficulty of separating such products from natural corundum. Microscopic examination is presented as the most reliable means of identification. Diagnostic internal features include remnants of the flux melt and platinum inclusions, while growth structures may closely resemble those found in natural sapphire, although subtle differences can aid identification. The paper illustrates these features with eight figures, six in color, and discusses their usefulness in distinguishing Chatham synthetic sapphires from natural stones.

corundum, treatments.6, irradiation, gems

Recently in New York, we were shown a ring containing a natural colorless sapphire that the client said had been a pleasant “Ceylon” yellow before a recent repair job. Dr. Kurt Nassau had suggested that the client bring the ring to us for the purpose of exposing it to X-rays. On two occasions in the past, Dr. Nassau had restored the color to red tourmaline—mistaken for ruby—that had lost its color due to overheating. In those cases, the color, apparently permanent, was restored using gamma rays. To control our experiment with the colorless sapphire, we exposed the ring and another colorless sapphire from our own collection. When the two stones reached a medium dark brownish yellow, we placed them in a sunny window for about four hours. Upon removal, our loose stone had become colorless again, but the ring stone had turned a pleasant yellow, which the owner stated resembled the original hue. Evidently, the natural color center differs from an induced center, although heat can render both colorless. We anticipate that the restored color will be permanent under normal conditions.

corundum, synthetic corundum.7, Ramaura, flux, gems

Bosshart presents the first gemological investigation of the newly introduced Ramaura synthetic ruby. Seven specimens ranging from intense red to pale violet-red were examined. Particular attention is given to microscopic inclusions and ultraviolet-visible absorption spectra, with significant differences observed between the strongly colored and paler material. The intense red specimens contained substantially more inclusions, while spectrophotometry revealed two distinct types of absorption behavior corresponding to the different color groups. Some Ramaura rubies showed properties sufficiently similar to natural ruby to make identification difficult, emphasizing the importance of microscopic examination and spectrophotometry in distinguishing this new synthetic material.

gems, pyroxene, orthopyroxene, enstatite, Kenya, East Africa, John Saul

Enstatite of yellowish-green colour from the region of the Mairimba Hill, Kenya, is described. The crystals have refractive indices of nx = 1.652, nz = 1.662, β = 0.010 and a density of 3.23 g/cm³, and owe their attractive colour to a content of 1.45% FeO and 0.22% Cr₂O₃.

gems, archaeology, archaeogemology, Saudi Arabia

This book is an introduction to the work carried out by us so far at Qaryat al-Fau; it is also a portrayal of the high level of civilisation which the Arabian Peninsula achieved during one particular period of its history. The University of Riyadh can claim to be the pioneer of archaeological research in the Kingdom of Saudi Arabia, as when work at Qaryat al-Fau first started, nothing had been undertaken elsewhere by Saudi nationals. The University, in its role as a centre of education and scientific research, found it entirely natural to support such an archaeological exploration. The work at al-Fau concerns our roots, and these are very deep; our recorded history extends back for thousands of years. The combined effort of our University and the Department of Archaeology and Museums in the Ministry of Education have, over the years, given scholars a clearer picture of the many and varied civilisations which occupied the Arabian Peninsula during the last few thousand years. Arabia was, after all, a meeting point between the early civilisations of China, India, Persia, Iraq, Syria, the Mediterranean world, Egypt, and the area which is now Ethiopia. It is possible to visualise Arabia as the centre of a planetary system with many forces and influences acting upon it; it was involved in give and take, influencing and being influenced by neighbouring civilisations which, although in many cases more advanced in several ways, had nevertheless often grown from the same roots as the civilisations of the Arabian Peninsula. There is no doubt that Arabia, as revealed by the archaeological work so far carried out, contains evidence of some of the earliest flowering of civilisation in the history of mankind. One particular manifestation was very much the product of Arabia itself. Its links with the ancient centres of civilisation were strong, for because of its geographical position, it was at various times the generating force for trade and trade routes, as well as a point of departure for successive migrations to the valley of the Tigris and Euphrates, Syria, and the Nile Valley.

gems, archaeology, archaeogemology, Africa, Egypt, color science, Egyptian blue

The bust of the famous Egyptian queen Nefertiti was made during the reign of her husband Amenophis IV–Echnaton (1364–1347 B.C.) in the XVIIIth Dynasty. There are many fascinating stories, more or less historical, about the life of Nefertiti and about the origin of the bust. This unique art piece was found in December 1912 in Tell El-Amarna (Middle Egypt) during excavations carried out by the German Oriental Society led by Ludwig Borchardt. In 1920 the bust was donated to the New Museum on the museum island (today East Berlin) by James Simon, who had financed the archaeological expedition. It was hidden at the end of World War II, found by American troops in a salt mine in what is now the German Democratic Republic, and transported to the “Art Collecting Point” in the former German-U.S. zone in Wiesbaden. From there the bust of Nefertiti was brought back to the Egyptian Museum in West Berlin. Since 1967 it has been one of the main attractions of this exhibition (Berl. Mus. No. 21300). The bust is about 0.5 m high and made of a soft limestone supplemented with plaster. It is richly painted and decorated, and overall its state of preservation is excellent (see cover). For decoration of the bluish crown and the collar, gold stripes and inserts made of colored frits and stones were used abundantly. Chemical analysis of the dyes and pigments used on the bust was first carried out by Friedrich Rathgen and published by Ludwig Borchardt in 1923. To confirm or refute Rathgen’s findings, we wanted to examine these pigments using some of the more modern analytical techniques that have developed since his experiments. We were especially interested in the composition of the blue pigment because of some previous studies we had made of ancient Egyptian blue pigments of various localities and dynasties. With special permission from the Egyptian Museum, it was possible to get small samples from the original object for our investigations.

corundum, ruby, sapphire, treatments.6, heat, gems

Following upon Nassau's 1981 article on the technical aspects of heat treating ruby and sapphire, the author reports his personal observations of the actual heat treatment process in Bangkok. He discusses the potential effects that this process can have on a stone—both positive and negative—and emphasizes the importance of the natural make-up of the stone itself to the success of heat treatment.

corundum, Thailand.12, gems

The article surveys the gemstones of Thailand, with particular attention to the country’s important corundum deposits. It discusses ruby and sapphire occurrences, their geographic sources, characteristic appearances, and aspects of mining and production. It provides an overview of Thailand’s position as both a producer and trading center for colored gemstones in the early 1980s.