beryl, emerald, Austria, gems

Gübelin investigates whether emeralds from Habachtal, Austria, possess characteristics that distinguish them from emeralds of other origins, combining a review of mining history and geology with measurements and detailed microscopic examination. He recounts the deposit’s reported exploitation from antiquity onward and the repeated difficulties encountered by later mining ventures. Its position at approximately 2,100 metres in the Hohe Tauern, hazardous access, prolonged winters, modest production, and short mining licences are presented as obstacles to sustained commercial development. The emerald-bearing zone lies near the contact between central gneiss and surrounding schists. Gübelin interprets its formation through contact metamorphism and the interaction of granitic residual solutions with neighbouring rocks, assigning the beryllium supply to granite and the chromium responsible for green colour to serpentinite. Biotite schist is the principal host, accompanied by tremolite, actinolite, chlorite, and talc-rich rocks; he draws parallels with emerald deposits in the Urals, India, and the Transvaal. Most local beryl is pale or greyish green, while only a small proportion displays fine emerald colour, and abundant inclusions commonly diminish transparency and value. Crystals generally show simple prismatic forms, sometimes flattened according to their orientation within the schist. Measurements on eleven specimens establish average refractive indices of approximately 1.591 and 1.584, birefringence near 0.007, and an average specific gravity of 2.74. Dichroism is generally weak, combining yellowish green and bluish green, and the absorption spectrum is typical of emerald. Chelsea-filter reactions range from pink to red; ultraviolet fluorescence is usually suppressed, attributed to iron, although some specimens fluoresce red and the response under a Stokes fluoroscope is more conspicuous. The principal diagnostic evidence comes from inclusions and internal fractures. Gübelin describes frequent basal cracks, intersecting fracture systems, healed fissures, and liquid-filled cavities or negative crystals, commonly containing two phases and forming dense featherlike patterns. Biotite is the most abundant mineral inclusion, occurring as isolated plates, clustered books, or material extending inward from the matrix, sometimes altered or strongly resorbed. Other identified inclusions include tremolite, tourmaline, apatite, epidote, sphene, and rutile. Emeralds associated with tremolite-bearing rocks are generally clearer and less fractured than those from biotite schist, though often more bluish, and contain green needles, rods, or blades that may cross the entire crystal, terminate internally, form bundles, or bend. Gübelin regards the appearance of these tremolite inclusions as especially characteristic of Habachtal and valuable for recognizing cut stones, while acknowledging resemblance to amphibole inclusions in Ural emeralds. Photomicrographs document the inclusion assemblages, supporting the article’s central connection between geological environment, internal features, and the assessment of geographic origin.

corundum, ruby, sapphire, inclusions.5, synthetic corundum.7, Burma.12, India.12, Kashmir.12, Thailand.12, Cambodia.12, Sri Lanka.12, USA.12, Montana.12, gems

Sinkankas: Unique among gemological monographs because of its very large number of inclusion photographs, taken by the author and clearly explained in the accompanying text. Preliminary chapters discuss inclusions in general, their types, formational causes, typical forms or accumulations, and inclusions in synthetic gem materials, glasses, and assembled stones. The work treats diamond, corundums, tourmalines, beryls, garnets, topaz, spinels, quartzes, peridot, moonstone, andalusite, kyanite, zircon, and fluorite. The color frontispiece shows inclusions in natural sapphire and ruby. A greatly enlarged color-plate version of this work, entitled Innenwelt der Edelsteine (1973), which see, provides essentially the same information, augmented with new material, but the present work continues in demand because it is more readily understood in some respects and more easily referred to. It is now rare. Review: Webster, The Gemmologist, 22, 1953, pp. 53–54, “cannot be overlooked … for the subject dealt with may be found in no other book studied in such great detail and from … a writer who has studied the subject so fully.” See also his comments in Journal of Gemmology, 4(2), 1953, pp. 78–80.

gems, inclusions, corundum, ruby, sapphire, beryl, emerald, spinel

E.J. Gübelin examines the diagnostic value of gemstone inclusions, extending his earlier general survey into a comparative account of internal features characteristic of particular gem species and localities. He argues that inclusion microscopy deserves a position alongside refractive-index measurement and absorption spectroscopy as a principal identification method, with applications extending beyond the separation of natural stones from synthetics and imitations. Improved dark-field illumination and a rotating specimen holder facilitate examination from different directions, allowing the observer to assess enclosed crystals, cavities, fluids, fractures, and their spatial relationships. The central principle is that diagnostic significance depends less on the isolated presence of an inclusion than on its recurrent appearance, morphology, arrangement, distribution, association with other internal features, and correspondence with minerals accompanying the host in its deposit. Numerous photomicrographs support descriptions organized principally by gemstone. Diamond inclusions include mineral crystals, enclosed diamonds, clouds, and fractures whose forms may preserve evidence of original growth surfaces and crystal orientation; Gübelin challenges the trade’s indiscriminate description of dark inclusions as carbon spots. Corundum receives detailed treatment, with contrasting inclusion assemblages attributed to Burma, Ceylon, and Siam. These include differing forms of silk, mineral crystals, zircon-related halos, liquid feathers, and opaque crystals associated with surrounding fluid features. Kashmir sapphire’s haziness is interpreted through extremely fine internal cracks or channels. Among beryls, the shapes and contents of liquid cavities, particularly three-phase inclusions containing liquid, gas, and crystals, are emphasized in emerald identification and geographical comparison. Aquamarine is discussed through fluid-filled channels and distinctive crystalline formations, while Gübelin acknowledges that similarly useful features had not been established for several other beryl colours. Garnet varieties illustrate the importance of inclusion arrangement: demantoid contains characteristic fibrous bundles, red garnets display three-dimensional distributions of needles, hessonite combines crystalline inclusions with a streaked internal appearance, and spessartite exhibits distinctive liquid-droplet feathers. Further examples include tourmaline trichites, ordered microscopic crystals in spinel, branching fissures associated with moonstone twin lamellae, angular structures in green metamict zircon, cleavage-related fissures in kyanite, and tetrahedral fluid cavities in fluorite. Gübelin recognizes that superficially similar inclusions can require considerable experience to distinguish and that some enclosed minerals remain unidentified. The article therefore offers selected diagnostic examples rather than an exhaustive inventory. It concludes that systematic study of internal mineral associations can unite practical identification with investigation of gemstone genesis, providing a productive field of collaboration among gemmologists, mineralogists, and crystallographers.

corundum, synthetic corundum.7, color.4, gems

A practical introduction to scientific gem identification written primarily for jewellers, dealers, and pawnbrokers without formal gemmological training. Drawing on his experience at the Precious Stone Laboratory of the London Chamber of Commerce, Anderson explains how simple instruments and observations can supplement traditional visual identification and distinguish natural gemstones from synthetics and imitations. The opening chapters describe the principles and practical use of the refractometer, double refraction, colour filters, dichroscope, specific gravity measurements, microscope, and spectroscope. Particular attention is devoted to detecting synthetic corundum through curved growth lines, gas bubbles, colour zoning, and the absence of characteristic natural inclusions, with additional discussions of synthetic spinel, synthetic emerald, glass imitations, and composite stones. Subsequent chapters provide systematic identification procedures for diamond, ruby, sapphire, emerald, opal, alexandrite, zircon, aquamarine, topaz, quartz, garnet, tourmaline, peridot, spinel, and numerous other gem materials, including translucent and opaque stones. Organic materials such as amber, tortoiseshell, coral, jet, and pearls are also examined, with methods for distinguishing natural, cultured, and imitation pearls. Throughout, Anderson emphasizes inexpensive, nondestructive tests, practical experience, and the use of several independent observations to establish reliable identifications. Numerous photomicrographs, diagrams, comparative tables, and an appendix of gem properties complement the text. Published during the Second World War, the book provides an important historical record of gemmological testing techniques and instrumentation available to the jewellery trade in the early 1940s, particularly the developing importance of microscopy, absorption spectroscopy, and the Chelsea colour filter.

corundum, ruby, sapphire, Thailand.12, Cambodia.12, inclusions.5, quality.10, gems

Ulrich Gühler surveys the properties, occurrence, mining, cutting, and trade of precious stones in Siam, combining published historical and scientific accounts with personal observations and more than twenty years of commercial experience. The study concentrates on sapphire and ruby, while also discussing zircon, black spinel, topaz, garnet, and unconfirmed reports of local diamonds. Introductory mineralogical descriptions address crystal form, hardness, specific gravity, optical behaviour, colour, inclusions, and defects, linking these characteristics to identification, cutting, and valuation. Zircon receives particular attention for the colour changes produced by heating under oxidising or reducing conditions and the subsequent instability of some treated stones. Historical references establish the long-standing recognition of Siamese gem resources, followed by regional accounts of Pailin, Chanthaburi, Trat, northern occurrences, and Bo Ploi in Kanchanaburi. The Bo Ploi discussion draws on repeated visits and earlier geological investigations, describing sapphire-bearing weathered material, associated black spinel, discoveries in the parent rock, fluctuating production, concession arrangements, and the hazards of speculative mining. Gühler outlines recovery through small pits, excavation, washing, and hand sorting, emphasizing the importance of Burmese and Shan miners and the uncertain rewards for both labourers and concession holders. The commercial section follows stones from rough parcels through cutting, sorting, bargaining, export, wholesale distribution, and retail sale. Colour, transparency, weight, rarity, brilliance, proportions, and visible flaws govern value, while attempts to preserve excessive weight during cutting can impair optical performance. Comparisons distinguish typical Pailin and Kanchanaburi sapphires and contrast generally darker Siamese rubies with Burmese material. A proposed numerical valuation scheme is offered cautiously as an aid to comparison rather than a definitive price formula. Tables document approximate Bangkok prices before, during, and after the war, with exchange-rate changes, hoarding, smuggling, and incomplete statistics complicating interpretation. Gühler also explains the commercially introduced “small carat” method of pricing zircon and criticizes its potential to obscure price increases. A final chapter considers Verneuil synthetic corundum, diagnostic curved growth lines and gas bubbles, risks of misrepresentation, and the continuing appeal of natural stones despite inexpensive manufactured alternatives. An appendix corrects his initial scepticism about synthetic star corundum, reporting B.W. Anderson’s confirmation that asterism is produced by fine rutile needles and describing features useful for detection. The study concludes optimistically that systematic exploration, improved organization, machinery, and investment could expand Siam’s gem industry and its contribution to national income.

corundum, Burma.12, Thailand.12, inclusions.5, gems

gems, amber, Burma, burmite, Sicily, Baltic Sea

An exceptionally comprehensive and learned survey of all phases of the knowledge of amber as then known, and holding its place as the preeminent work on the subject in the English language until the recent appearance of P Rice's Amber: The Golden Gem of the Ages, 1980, which see. Rice's work contains much new information but does not entirely supersede Williamson's highly interesting monograph. The first chapters treat amber in general, discuss classical allusions, nomenclatural problems, the amber routes of antiquity, and the place of amber in anthropology and archeology. Amber is next considered as a substance with remarks on the geology of deposits, and the many inclusions of plant and animal life that have been found in it. Rather strangely, the flow of information on the natural history is here interrupted by a chapter on amber in art, after which the text returns to discussion of the famous amber deposits of the Baltic region, also those in England, and then again, rather jarringly, amber is discussed as a medicinal material and uses in amulets, or other lorical applications. However, from this point, the text treats amber in Sicily, Romania, and Burma, remarks on the similar-sounding ambergris, describes other fossil resins, the making of amber varnish, and amberoid or pressed amber. The bibliography is very extensive, possibly the largest to be assembled up to that time, but the entries lack paginations, and some lack the names of journals from which taken, and others are trivial. Rev K Andree, Bernstein-Forschungen, 3, 1933, 212. Copies are scarce and still much in demand. There is a reprint of same date in sepia-brown cloth, the gold spine Jett usually tarnished to copper.

corundum, sapphire, Queensland, Australia.12, gems

Sinkankas: The first geological-mineralogical report on the famous Anakie gem corundum field and almost as interesting for its remarkable color plates as for its text. Describes general geology, details on specially productive areas, advice to prospectors, and much incidental information also useful to the lapidary and gemologist as washing sapphire-bearing gravel, the crystal forms of corundum, zircon and spinel, a note of a diamond discovery at one of the localities, a list of minerals found, historical notes, notes on foreign deposits, and descriptions of the plates. Though crudely executed, the plates depict sapphire crystals in various forms and inclusions in them, and appear to be the first colored illustrations of Anakie sapphires. Among the color plates is one that shows corundum faceted gems, brilliant-cut, in a variety of hues. An extremely scarce report.

jade, jadeite, fei cui, nephrite, Burma, China, gems, Broken Bangle

Bishop presents a preliminary collection of scientific and historical studies of jade, undertaken with the cooperation of mineralogists, chemists and Chinese scholars and drawing extensively on specimens in his collection. The volume distinguishes jadeite and nephrite by their chemical composition, mineral structure and physical properties, while examining the colours, translucency, optical behaviour and inclusions of both materials. Microscopic investigations describe their granular and fibrous textures, and experimental studies measure hardness, specific gravity, resistance to impact, compression and tension, and sonorousness. Particular attention is given to jade’s exceptional toughness and its relationship to the interlocking structure of its constituent minerals. Contributions by J.P. Iddings, F. W. Clarke, L.V. Pirsson and others explore chemical constitution, geological origin and possible transformations between jade-bearing rocks, presenting interpretations within the scientific knowledge then available. Henry S. Washington surveys geographical occurrences, distinguishing deposits observed in place from transported boulders, worked objects and uncertain locality reports, and discusses their implications for ancient trade and cultural connections. George Frederick Kunz examines minerals confused with jade, artificially coloured substitutes and glass imitations, outlining methods of discrimination. The historical sections concentrate on China: Stephen W. Bushell discusses jade-producing regions, varieties, literature, imperial collecting and ritual uses, and translates T’ang Jung-tso’s Yü Shuo, a discourse addressing sources, value, colours, antiquities, objects and the employment of jade by emperors and the state. Its supporting bibliography identifies 71 Chinese works. A concluding account associated with the artist Li Chêng-yuan describes contemporary manufacturing processes, from preparing abrasive sands and sawing rough blocks to shaping, hollowing, drilling, openwork carving and polishing. Together, these contributions connect jade’s mineralogical properties with its practical working, aesthetic appreciation and cultural significance.

ruby, sapphire, corundum, Burma.12, geology.11, gems

Brown and Judd present a detailed investigation of the ruby deposits of Burma, based on geological observations and specimens collected by Brown and mineralogical and petrographic examination by Judd. They describe the occurrence of ruby at Mogok and neighboring localities, emphasizing its association with crystalline limestone and the minerals accompanying it, and distinguish primary occurrences from the secondary gem-bearing deposits produced by weathering and erosion. Microscopic study is used to investigate the structure of corundum and the numerous inclusions, alterations, and secondary minerals developed within or around the crystals. Particular attention is given to the transformation of corundum into other minerals and to the evidence these changes provide concerning the geological history of the ruby-bearing rocks. The authors discuss the probable origin of Burmese ruby, the metamorphic processes affecting the deposits, and the subsequent concentration of resistant corundum crystals in superficial deposits. The paper is an important early study combining field geology, mineralogy, and petrography to explain the occurrence, origin, and alteration of the rubies of the Mogok district.