gems, early lapidaries, Marbode

Wiemann presents a critical edition and German translation of Johannes Cuspinianus’s Latin commentary on Marbod of Rennes’ Liber lapidum, a medieval didactic poem describing sixty stones and their supposed natural, medicinal and magical properties. The study is based principally on Vienna manuscript Cod. 5195, with comparison to the editio princeps of 1511, which Cuspinianus prepared for publication. It makes the Renaissance commentary accessible through a critically established Latin text and facing or accompanying German translation and provides material for studying the transmission and early printed reception of Marbod’s lapidary. The work is particularly relevant to the history of gemological and mineralogical literature because it documents how a major medieval lapidary was interpreted and transmitted by an early-sixteenth-century humanist scholar.

gems, jade, jadeite, fei cui, Mesoamerica, Mexico, Guatemala, Costa Rica, Mayans, Olmecs, Aztecs, archaeology, history, archaeogemology, Pre-Columbian jade; Costa Rica; Maya; exchange; iconography, lapidary

gems, jade, jadeite, fei cui, Mesoamerica, Mexico, Guatemala, Costa Rica, Mayans, Olmecs, Aztecs, archaeology, history, archaeogemology

gems, beryl, emerald, Brazil, Santa Terezinha

Bank and Petsch report a newly recognized emerald occurrence near Santa Terezinha de Goiás, Brazil, describing the locality and the characteristics of the emerald material being produced there. The brief paper discusses the geological occurrence of the emeralds and their association with the host rocks, together with observations on the appearance and gemological characteristics of the crystals. It represents an early gemological report on Santa Terezinha, which subsequently became one of Brazil’s important emerald-producing districts.

corundum, Nepal.12, gems

garnet, Umba Valley, Tanzania, gems

Gübelin examines the internal features of garnets from Tanzania’s Umba Valley, a locality producing garnets across the pyrope–almandine–spessartine compositional range. The paper documents and illustrates their characteristic inclusions and considers their value for gemological identification and for interpreting the conditions under which the garnets formed. Later inclusion literature specifically records crystallographically oriented networks and star-like arrangements of rutile needles in Umba Valley garnets, citing Gübelin’s work on this material.

corundum, ruby, sapphire, quality.10, gems

gems, general gemology

Sinkankas from M. O’Donoghue: The bulk of this book consists of an alphabetical listing of stones, preceded by introductory chapters on gem testing. Much, if not all, of this section appears unchanged from the fourth edition, though some additions have been made to the alphabetical section. A large portion of each entry is devoted to discredited names, effectively giving them an undeserved extension of life—a practice that is hardly scholarly. Unfortunately, much of the material is inaccurate or carelessly presented. This is a pity, as the book is well-produced, and the colored illustrations—though largely taken from H.-J. Schubnel’s Pierres Précieuses dans le Monde—are still effective despite their reuse. The entire text would benefit greatly from revision by someone familiar with modern gemmology.

corundum, synthetic corundum.7, gems

Gübelin and Knischka describe a new gem-quality synthetic ruby produced by Paul O. Knischka using a proprietary “gradient technique” involving supersaturation and controlled cooling. The resulting crystals have an unusual nearly isometric or pseudocubic habit and exceptionally numerous well-developed, undamaged crystal faces, with examples possessing 32 or 38 faces. The authors compare several types of Knischka synthetic ruby with natural and Verneuil synthetic ruby, examining crystal morphology, trace-element chemistry, optical and gemological properties, fluorescence, and inclusions. In color and general appearance the material closely resembles natural ruby, although it tends toward a more violet red; refractive index, birefringence, and other standard properties offer little assistance in separation. Microscopic features include folded or feather-like inclusions, color zoning, two-phase inclusions, negative crystals, and occasional metallic platelets, some of which can resemble features in natural stones. The study emphasizes the increasing difficulty of distinguishing high-quality synthetic ruby from natural material and the potential diagnostic value of inclusions and trace-element composition.

gems, jade, Chinese jade, nephrite, Chinese jade carving, jadeite, fei cui, Burma, New Zealand