corundum, quality.10, Tajikistan.12, spinel, gems

Meen describes and documents the largest and most important gemstones in the Iranian Crown Jewels, drawing upon his examination of the collection in Tehran. Particular attention is given to exceptional diamonds, emeralds, rubies, sapphires, spinels, and other large gems, with discussion of their weights, dimensions, colors, forms, and settings. The article places these stones within the extraordinary accumulation of loose gems and jeweled objects assembled by successive Persian rulers and comments on problems of identification and nomenclature among historically celebrated stones. Illustrated with photographs of major specimens, the paper provides an important gemological record of outstanding stones in the Iranian treasury and complements the broader historical documentation of the Crown Jewels of Iran.

beryl, emerald, gems

Thirty infrared absorption lines in beryl between 1500 and 11,000 cm⁻¹ are assigned to vibrations of two types of water and to CO₂, all in the axial voids of the structure. The spectrum of Type-I water arises from molecules which are capable of libration and are located between the silicate rings which make up the crystal. The spectrum of Type-II water arises from molecules in the same sites, but with alkali ions nearby. These molecules are also capable of libration, but at a higher frequency. The Type-I molecules have their C₂ symmetry axes perpendicular to the crystal C₆ axis, while the Type-II molecules have their symmetry axes aligned parallel to the crystal C₆ axis. The CO₂ molecules are oriented with their long axes perpendicular to the crystal C₆ axis. Modification of the spectra by heat and hydrothermal treatments was not feasible, and the identity of the alkali ions apparently does not influence the Type-II spectrum.

corundum, Madagascar.12, gems

Besairie presents a comprehensive survey of the mineral deposits and mineral resources of Madagascar, synthesizing geological investigations, mining records, and exploration carried out throughout the island. The work describes metallic and non-metallic deposits according to their geological setting, mineralogy, distribution, and economic importance, with attention to gold, chromite, iron and manganese ores, copper, nickel, lead, zinc, uranium and radioactive minerals, graphite, mica, quartz, feldspar, beryl, and numerous other mineral substances. Considerable attention is given to Madagascar’s pegmatites and their exceptionally diverse mineral assemblages, including beryl, tourmaline, spodumene and other lithium minerals, and associated rare-element minerals. Gem materials are treated within the discussion of individual deposits and mineralized districts, including beryl and emerald, corundum and sapphire, tourmaline, garnet, quartz, and other ornamental stones. Besairie relates the deposits to Madagascar’s regional geology and discusses their occurrence in the Precambrian crystalline basement, pegmatites, metamorphic rocks, intrusive complexes, and younger formations. Numerous locality descriptions and references to earlier exploration and exploitation make the volume both a synthesis of Madagascar’s economic geology as understood in the mid-twentieth century and an extensive geographical reference to the island’s known mineral occurrences.

gems, synthetic beryl, synthetic beryl, emerald, Gilson

Description of Gilson synthetic emeralds.

gems, Brazil, emerald, topaz, quartz

Review of the gem deposits of Brazil.

beryl, emerald, Rhodesia, Sandawana, Zimbabwe, gems

gems, emerald, beryl, synthetic emerald, hydrothermal synthesis, crystal growth

First report of beryl synthesis using hydrothermal growth method.

corundum, history.1, gems, jade, Fischer-Other, early lapidaries

According to Caley and Richards (ibid., 4), the treatise is a set of notes, possibly taken down by a student listening to lectures delivered by Theophrastus, but “safely assumed to represent the actual views of Theophrastus, and he may reasonably be considered the author.” On the other hand, Eichholz (ibid.) is firmly of the view that the treatise is Theophrastus himself, and that it is not a fragment, as has been suggested numerous times, but a complete, though short, work. Theophrastus’ treatise, commonly called the Peri Lithon, or “Concerning Stones,” commences with speculations as to the origins of stones and discusses their distinctive properties as well as the means by which differences among them may be elucidated. This is followed by a rather rambling description of numerous gemstones and earths, excepting metallic minerals and metals, which are stated to have been described elsewhere in a treatise now lost. All of the matter is presented tersely and is almost entirely free of superstitious lore, except for the emerald, for which it claims that it refreshes the eyesight upon gazing and that an emerald placed in water colors it green. F. D. Adams (Birth and Development of Geological Sciences, 1938, 19) notes that “it differs entirely in its style and content from any other work upon this subject written in classical times—in fact, no other work at all resembling it appeared until later on in the Middle Ages. It remained for 1800 years a most valuable and authoritative work on minerals, referred to and quoted by all, and shows that even at this early time there existed, probably among miners, quarrymen and other men engaged in the technical trades and industries, a body of knowledge of mineralogy, especially on its practical side, which had been drawn upon by Theophrastus in the compilation of his work.” Adams further notes that Pliny must have had a more complete version of the treatise because of mentions of stones that are not now in the Peri Lithon, but this is refuted by Eichholz as noted above. H. Tertsch (Das Geheimnis der Kristallwelt, 1947, 31–4) also provides illuminating remarks on the treatise, suggesting that it reflects the views of Aristotle, his mentor. The gemstone content of Peri Lithon is not large but important for those ornamental and precious materials that it does name—namely, marbles and calcite onyx, lapis lazuli, obsidian, and other massives, and also emerald, sard, garnet, adamas (probably corundum), amber, rock crystal, and others—all of which are carefully examined by Caley & Richards and by Eichholz, who make identifications where possible. Both authorities offer much ancillary material which makes rewarding reading as well as providing lists of printed editions of Peri Lithon from which I have freely drawn much of the information below on not personally examined.

gems, pearls, precious stones, jewelry

Hatem presents a popular but substantial survey of pearls and precious stones, combining gemological information with history, geography, mining, trade, and famous gems. She discusses the principal gemstones, including diamond, ruby, sapphire, emerald, and pearl, describing their formation, physical characteristics, important producing regions, methods of recovery and cutting, and their place in commerce and jewelry. Historical accounts and anecdotes trace the fascination with precious stones from antiquity to the modern period, including celebrated jewels, royal treasures, discoveries, and the development of major gem-producing districts. Synthetic gemstones and attempts to manufacture diamond are also treated, including Moissan’s experiments. Pearls receive extensive attention, with discussion of natural pearl fisheries, cultured pearls, mollusks, formation, grading, and important producing regions. Written for the general reader rather than as a technical gemological manual, the volume brings together scientific explanations and historical material and is extensively illustrated, with 78 figures and a map in the text and 103 illustrations on plates.

corundum, synthetic corundum.7, stars, gems

THE aluminum oxide known as corundum has several varieties that have been used as gem materials since ancient times. These include the red variety called ruby, the blue variety sapphire, and the asteriated types of ruby and sapphire. Asteriated sapphire was known to the ancients under the name of astrios, and descriptions of this gem were given by Pliny and other early writers. The relation of these gem materials to each other as varieties of a single species, corundum, was first clearly established by Haüy in 1805 and J. M. Güthe1 in 1809. Natural gem corundum is obtained principally in Ceylon, Siam, Burma, India, and Australia. Star sapphires and rubies always have been highly prized and in recent years have become particularly popular in the United States. Natural star rubies of large size and fine quality are extremely rare and rank with large and fine emeralds and diamonds as the most valuable of gem stones. Interest thus attaches to the recent success in commercially synthesizing star sapphires and rubies of a size and perfection unmatched by nature.