gems, glyptic, engraved gems, agate, cameo, intaglio

Riederer provides the mineralogical identification of the materials used for the engraved and magical gems catalogued by Hanna Philipp in Mira et Magica. The contribution supplies the scientific basis for distinguishing the various natural stones and artificial materials represented in the collection and discusses the problems inherent in identifying ancient gem materials, particularly where traditional archaeological or gemological names do not correspond precisely with mineralogical nomenclature. The results complement Philipp’s archaeological and iconographic catalogue by establishing the actual materials from which the objects were made. A later archaeometric discussion specifically uses the Mira et Magica collection to illustrate how different investigators could arrive at differing identifications because of both analytical and nomenclatural problems.

gems, bibliography, book collecting, books on gems and jewelry, mineralogy

Nigel Israel: This is an extremely useful little book (booklet would, I think, be a better description) by the Curator of Earth Sciences at the British Library. Starting with a general preface and introduction, it attempts, quite successfully, to list the more important works on gemmology under various categories, including encyclopaedic works, general comprehensive surveys, gem testing, gem testing instruments, quick reference publications, textbooks, synthetic gemstones, fashioning, works on individual species, jewellery, gemstones of particular localities, bibliographies, abstracts, journals, gemstone prices, guides to collections, and regalia. The works are listed with their publication details, including if and where they are held by the British Library, and, in many cases, with helpful descriptions by the author. The book ends with a useful index, followed, inexplicably, by two pages of beryl and corundum crystal diagrams. The literature of gemmology is extremely large, so the selection is necessarily a personal one by the author, and many people will likely be surprised by the omission of some of their favorite works. The reviewer was personally most surprised by the exclusion of Diamonds and Precious Stones by Emanuel (1865 and 1867), as this book contains an extremely extensive bibliography of historic books on gemstones. However, despite the unfortunately high price of a soft-covered booklet of little more than photostat quality, I would certainly recommend The Literature of Gemstones (together with the author’s companion work The Literature of Mineralogy) to anyone interested in gemmology.

beryl, synthetic beryl, emerald, synthetic corundum, gems

Gübelin reviews the diagnostic properties of several recently introduced synthetic gemstones and the problems they pose for separation from their natural counterparts. Emphasis is placed on the combination of conventional gemological properties with microscopic examination of inclusions and growth structures, supplemented where necessary by spectroscopic and other analytical methods. The article discusses characteristic features of newer synthetic materials, particularly synthetic corundum and emerald, and shows that physical constants alone may be insufficient for identification as manufacturing techniques increasingly reproduce the appearance and properties of natural stones. Gübelin stresses the diagnostic importance of flux residues, metallic inclusions, growth zoning and other internal features associated with particular synthesis processes. The paper summarizes practical criteria by which these newer products can be recognized in gemological testing.

gems, early lapidaries, early gemology, early mineralogy, Chaucer, history of gemology, nomenclature, lore, medicinal use

Chaucer's corones tweyne" of Troilus, II, 1935 has been variously interpreted as the mythical stone "ceraunius," the papal tiara, and St. Cecilia's crowns. The two-crown motif should be seen in the context of marriage and martyrdom. Matheolus' Lamentations provides the exact source and inspiration for Chaucer's use of the two-crown motif: Troilus' chastity and fidelity in his marriage with Criseyde bestowed the first crown on him; his heroic death on the battle field in defence of the fatherland won for him the second crown."

beryl, synthetic beryl, emerald, gems, SEM

Hofmann, Schrader and Stender describe applications of scanning electron microscopy (SEM) to gemological research, emphasizing its usefulness for examining surface structures and extremely small features beyond the practical resolution of conventional gemological microscopy. Examples illustrate how the technique can reveal the morphology of inclusions, growth and dissolution features, fracture surfaces, and other microscopic structures relevant to gemstone investigation. When combined with electron-beam microanalysis, SEM also permits localized chemical characterization of minute inclusions or surface features. The brief article demonstrates the value of SEM as a complementary research technique where conventional optical microscopy alone provides insufficient morphological or compositional information.

opal, Mexico, gems

Gübelin describes the opal deposits of Mexico, concentrating on the important occurrences in Querétaro and their characteristic transparent to translucent precious and fire opals. He discusses the volcanic geological setting, occurrence of opal in cavities and fractures in rhyolitic rocks, mining and recovery of the material, and the considerable range of body colors and play-of-color displayed by Mexican opals. Particular attention is given to the internal characteristics of the stones, including mineral and fluid inclusions, and to the differences between Mexican volcanic opal and opal from other major producing regions. The article provides both a description of the deposits and a gemological characterization of their products. Gübelin’s article is subsequently cited specifically for opal from the Carbonera mine at La Trinidad, Querétaro.

corundum, synthetic corundum.7, Ramaura, synthetic garnet, gems

Gübelin describes two recently introduced artificial gem materials: Ramaura flux-grown synthetic ruby and yttrium gallium aluminate (YAG), the latter marketed as a green imitation of tsavorite garnet. The first portion discusses the manufacture and gemological properties of Ramaura ruby and emphasizes microscopic features useful for separating it from natural ruby, particularly characteristic flux residues and growth-related inclusions. The later installments treat yttrium gallium aluminate, describing its physical and optical properties and characteristic inclusions. The green material has a high refractive index and specific gravity and contains distinctive reddish-brown flux inclusions and wispy veil-like features. The series illustrates the importance of inclusion microscopy in recognizing artificial gem materials whose appearance may closely resemble natural gemstones. Contemporary abstracts confirm that the second installment concentrates on characteristic inclusions and the third on the physical and optical properties and inclusions of yttrium gallium aluminate.

gems, early lapidaries, early gemology, early mineralogy, Albertus Magnus, early English lapidaries

feldspar, gems

Bridges, Graziani and Gübelin describe a newly recognized gem-quality feldspar from Kioo Hill, Kenya, occurring in the central portions of larger feldspar crystals in a kyanite-bearing pegmatite associated with vermiculite and quartz. Mineralogical and chemical investigation identifies the material as a low-temperature albite with peristerite structure. The pale blue to greenish material has refractive indices of approximately 1.531–1.539, birefringence 0.008, and specific gravity 2.623 ± 0.002. The study discusses its occurrence, composition, crystallographic structure and gemological properties, establishing the material as an unusual gem variety of sodic plagioclase. The paper includes eight color figures, four diagrams and two tables.

gems, jade, pyroxene jade, fei cui, Guatemala, Mesoamerica, Nicaragua, Mexico, Honduras, Costa Rica, archaeogemology, Olmecs

Tibón examines jade and other greenstones in ancient Mexico primarily through their religious, symbolic, linguistic, and cultural significance rather than as a mineralogical study. Central to the book is the Nahuatl concept of chalchihuitl, encompassing precious green stones whose value extended far beyond ornament. Drawing on early colonial chronicles, indigenous traditions, mythology, place names, and archaeological material, Tibón explores associations of greenstone with water, vegetation, fertility, life, wealth, divinity, and supernatural power. He discusses its use in ritual objects, offerings and personal ornaments, as well as traditions concerning the discovery and recognition of chalchihuites. The work is especially useful for understanding the cultural concept of “jade” in Mesoamerica, where indigenous terminology did not necessarily correspond to modern mineralogical definitions. Later Mesoamerican scholarship continues to cite the book in discussions of the symbolism and cultural valuation of jade and greenstone.