corundum, beryl, emerald, inclusions, synthetic beryl, emerald, gems

This illustrated series presents gemstone inclusions as practical evidence for identification, distinguishing natural from synthetic stones, and interpreting the conditions under which gems formed. Drawn from Gübelin’s photomicrographic studies and a collection of Kodachrome transparencies supplied to the Gemological Institute of America, the installments combine explanatory text with photographs and descriptive captions. Microscopic examination, particularly with dark-field illumination, reveals structures that may be overlooked or misinterpreted with a loupe. The sapphire section illustrates oriented needles and silk, angular growth zoning, mineral crystals, fluid cavities, and featherlike networks. Examples include hematite plates, enclosed corundum crystals, and cavities containing liquid and gas. These features are compared with curved growth striae and gas bubbles in synthetic sapphire. Gübelin cautions that appearances can be deceptive: natural cavities may resemble bubbles, while the curvature of synthetic growth lines may be difficult to recognize within a small field of view. The ruby installment similarly contrasts natural rutile arrangements, straight structural features, mineral inclusions, and fluid-related formations with curved striae and concentrations of gas bubbles in synthetic material. Zircon inclusions surrounded by halos and intersecting rutile needles illustrate characteristic internal features of individual specimens from Sri Lanka and Myanmar. The emerald section describes enclosed crystals, irregular cavities, and inclusions containing liquid, gas, and a solid phase, while comparing these with wispy formations and other internal features observed in synthetic emeralds. The diamond installment demonstrates the importance of illumination when interpreting dark inclusions: objects commonly regarded as black or carbonaceous may prove to be transparent crystals when examined appropriately. Photographs show enclosed crystals, including diamond, together with cleavage features and fractures associated with inclusions or extending inward from the surface. Subsequent installments broaden the survey to additional sapphires and other gem materials. Illustrated examples include fine networks of channels, negative crystals, mineral plates, zircon-associated halos, liquid inclusions with mobile bubbles, and cavities containing separate liquids. Topaz and tourmaline provide further examples of fluid-bearing inclusions, while the concluding selection extends the illustrated material to emerald, peridot, quartz, garnet, and moldavite. Biotite flakes in peridot and fibrous actinolite in quartz demonstrate the variety of solid inclusions; a fluid-bearing negative crystal in citrine reproduces the host’s prismatic form. Throughout the series, the diagnostic value lies in the combined character, arrangement, and appearance of internal features rather than in an isolated resemblance. Gübelin advocates making inclusion study an early part of gem examination, potentially preceding routine measurements of physical and optical properties. The series also emphasizes the scientific and aesthetic interest of microscopic structures, presenting gemstone interiors as records of mineral growth and subsequent events as well as aids to identification.

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

Sinkankas: Ch. 8, p. 283–311, on “Jade and other semiprecious stones,” with illustrations for the same being in the plates volume, Pls. 235–58 (not seen). Most of this text treats jade, its nature, types, and artistic significance, then describes the many objects depicted according to their artistic merits. Other gemstones are rock crystal, turquoise, obsidian, serpentine, amber, calcite onyx, and cryptocrystalline quartz varieties.

geology, gems

Gübelin presents a schematic introduction to gemstone formation and deposits, using a circular diagram and an element-based table to make geological relationships more accessible to students of gemology. He emphasizes that such summaries necessarily simplify a complex subject but can clarify the individuality of gemstones, guide the practical study of deposits, and provide a foundation for further investigation. The classification distinguishes primary mineral formation from ascending solutions, termed magmatic in a broad sense, from secondary growth and concentration associated with decomposition, sedimentation, and metamorphism. Primary processes are subdivided into liquid-magmatic, pegmatitic and pneumatolytic, and hydrothermal and volcanic-exhalative categories. Secondary categories comprise chemical sediments derived from the atmosphere or hydrosphere, residual deposits produced through decomposition and metamorphism, and mechanically concentrated sediments, particularly alluvial deposits. The circular diagram places deposit types outside the circumference and representative gem materials within the corresponding sectors. Minerals occurring in more than one geological setting cross sector boundaries; corundum, spinel, and garnet are specifically identified as examples with multiple modes of occurrence. Related minerals are grouped according to chemical composition or paragenesis, while the more important gem materials receive typographical emphasis. Gübelin explains that the diagram favors practical usefulness over strict genetic classification. Thus, amber and jet are placed among metamorphic formations, while pearls and corals appear among chemical sediments, although he explicitly recognizes their organic origin. The accompanying table develops the survey through chemical elements, linking important minerals with magmatic, sedimentary, residual, and metamorphic settings. It includes familiar gems such as spodumene, tourmaline, beryl, chrysoberyl, corundum, diamond, quartz, opal, zircon, turquoise, and garnet, together with less common ornamental minerals and several metallic minerals. Separate columns indicate the different processes through which these materials may form or become concentrated. Notes draw attention to the production of aluminum-rich residues by weathering and their subsequent metamorphic transformation, the role of atmospheric carbon in carbonates and organic materials, and the redistribution of certain minerals into alluvial deposits. The inclusion of rare elements requires reference to some uncommon gem materials, but the author stresses that neither the mineral list nor the deposit classification is exhaustive. Together, the diagram and table offer a condensed teaching aid connecting gemstone chemistry, mineral associations, formation processes, and economically relevant occurrences, intended as a starting point for more detailed geological study.

corundum, synthetic corundum.7, Verneuil, Linde, gems

This company release describes the establishment of American synthetic sapphire production in response to wartime disruption of European supplies and increasing demand for jewel bearings in military and industrial instruments. Previously dependent on manufacturers in Switzerland, France, and Germany, the United States faced shortages despite stockpiling during 1939 and 1940. In autumn 1940, the government invited qualified domestic companies to develop production, and Linde Air Products Company undertook experimental work leading from a single laboratory furnace to commercial manufacture. The article reports that, eighteen months after beginning, Linde informed the War Production Board that it could supply colorless sapphire in any reasonable quantity. Production was then devoted entirely to essential industrial and military requirements. The manufacturing account outlines the Verneuil process, in which purified alumina powder passes through an oxygen–hydrogen flame and accumulates on a pedestal as a crystalline boule. Appropriate coloring agents produce ruby or colored sapphire, while controlled growth and slow cooling are necessary to obtain usable material. The company describes its progress through experimentation without European specialists available to supervise the work. An illustrated sequence contrasts a shattered, opaque 14-carat boule from December 1940 with the first clear 20-carat product, a representative commercial boule of approximately 200 carats, and an exceptional recent example weighing about 350 carats. Synthetic corundum’s principal advantages for bearings are presented as high hardness, uniformity, and resistance to wear, supporting prolonged accuracy in delicate mechanisms. Regular boule dimensions and relatively defect-free material permit standardized cutting, reduce waste, and offer economies compared with natural sapphire. A comparative table gives Mohs hardness and Knoop microhardness values for several materials, including natural and synthetic sapphire, and records differences according to crystal orientation. The discussion also notes that natural and synthetic corundum share the same basic chemical composition and that coloring agents have little effect on refractive index or specific gravity; small hardness differences require specialized equipment to measure. Although colorless sapphire dominated wartime production, ruby had also been manufactured, and fine colored material had been produced experimentally. Broader production of colored sapphire and synthetic spinel was anticipated after the war. Proposed peacetime applications extend beyond jewelry and bearings to electrical insulators, injector and burner nozzles, thread guides, and special abrasives, drawing on sapphire’s chemical resistance, thermal properties, and dielectric behavior. The release concludes with the expectation that expanded mechanization, domestic cutting, and a growing skilled workforce would establish a lasting American sapphire manufacturing industry.

gems, history of gemology, Roman, Rome, Greek, Greece, history of mineralogy, history of science, Arabic mineralogy

Rackham’s Loeb Classical Library edition presents Books 3–7 of Pliny the Elder’s Natural History in parallel Latin and English texts. These books comprise Pliny’s geographical and ethnographical survey of the known world: Books 3–6 describe Europe, Africa, and Asia, including the Mediterranean lands, the Near East, India, and regions beyond, while Book 7 turns to humanity, discussing human characteristics, unusual peoples, remarkable births, longevity, exceptional physical and intellectual abilities, inventions, and other notable features of human life. Pliny draws extensively upon earlier Greek and Roman authorities, travelers, administrators, and geographical writings, preserving a large body of ancient geographical and ethnographic information, often intermingled with reports of marvels and fabulous peoples. For the history of gems and precious materials, these books provide geographical context for the regions from which luxury goods and mineral products reached the Roman world, although Pliny’s systematic treatment of stones and gemstones occurs later in Book 37.

gemology, asterism, phenomena, gems

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

Gübelin’s three-part study investigates the geographical identification of sapphires from Kashmir, Burma, Siam, and Ceylon, emphasizing microscopic inclusions as records of differing geological conditions. Reference specimens were obtained from selected dealers trading directly with the producing regions, while Ceylon’s fancy-colored sapphires supplied additional comparative material. The introductory discussion reviews characteristic colors, chemical differences, luminescence, refractive indices, and density, but cautions that these properties generally provide indications rather than certain determinations of origin. Comparative emission spectra of Burmese and Ceylon sapphires are interpreted in relation to their iron and titanium contents. Luminescence under cathode rays and ultraviolet radiation varies among the four sources, although exceptions and inconsistent responses limit its diagnostic value. Small differences in refractive index and specific gravity are likewise considered insufficient for confident identification alone. Microscopic examination forms the principal basis of the regional comparisons. Kashmir sapphires exhibit a characteristic haze that resolves under magnification into delicate veils of wavy, intersecting filaments arranged in hexagonal patterns. Gübelin distinguishes these from rutile needles, describing them instead as minute fissures or hollow tubes. Other Kashmir inclusions comprise thin films bordered by irregular networks of liquid-filled channels extending into individual droplets; their appearance changes as the stone is tilted. Burmese sapphires are characterized chiefly by short rutile needles densely distributed or grouped into patches, clouds, and zones. These follow the host’s crystallographic directions and intersect at 60° and 120° when viewed along the optic axis. Larger, well-formed rutile crystals and occasional curved liquid-filled cavities containing mobile gas bubbles are also described. Siamese sapphires are reported to lack rutile and instead contain broad, flat, loop-like fluid inclusions associated with opaque, approximately hexagonal features interpreted as resorbed crystals or negative crystals. Additional characteristics include brown material attributed to iron compounds, recrystallized inclusions in hexagonal arrangements, checkered twinning lamellae, and rows of script-like or arabesque fluid inclusions. Ceylon sapphires display a greater variety and generally less orderly distribution of inclusions. Their rutile needles are notably longer, sparser, and more widely spaced than those in Burmese material. Characteristic fluid feathers and flags comprise numerous tubular or wormlike cavities extending into isolated droplets, often with mobile gas bubbles; Gübelin identifies their liquid as carbon dioxide on the basis of his own investigations. He also describes scattered minute mineral inclusions, broad irregular fluid-filled tubes, and brown zircon crystals surrounded by pleochroic radiation halos. These zircons are regarded as particularly useful indicators of Ceylon origin, whereas accessory minerals occurring across several sources provide less decisive evidence. The study concludes that reliable interpretation requires extensive experience with numerous specimens and that photomicrographs offer a useful means of documenting the observed characteristics.

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

To the long-established list of analogues to Chaucer’s House of Fame, I propose still another: the apocalyptic vision of St. John in the New Testament. Though largely lacking in direct verbal similarities, the Revelation of St. John presents numerous compelling parallels that cannot be dismissed as mere coincidence. The sparse details from Ovid, Vergil, and Boethius are acknowledged to fall short of accounting for the grandeur of Chaucer’s portrayal of Lady Fame in Book III. Rambeau’s argument that Chaucer modeled his goddess on the Virgin Mary as depicted in Dante’s heaven is unconvincing, given how scattered and dissimilar the cited resemblances are. Cummings has thoroughly refuted the identifications by Koeppel and Child of Chaucer’s Fame with the Gloria del popolo mondano in Boccaccio’s Amorosa Visione. Evidence from the poem itself supports the view that Chaucer had the vision of St. John in mind when composing the palace of Fame. In describing the enthroned goddess, Chaucer draws on Vergil’s image of the many-eyed deity (Aeneid IV, 180–183), a detail that recalls the Revelation’s account (IV.6) of the four beasts “full of eyes before and behind,” which Chaucer explicitly references: “the bestes foure / That Goddes trone gunne honoure / As John writ in th’ Apocalips” (House of Fame, 1384–85).

gemology, asterism, phenomena, gems

gemology, physical properties, gems