gems, history of gemology, history of mineralogy, Arabic mineralogy, history of science, Greek science, astronomy

Through the increased use of Carbon-14 dating in West African archaeology, it is now widely accepted that iron was known to the ancient Nok peoples of present-day Ghana and Nigeria during the pre-Christian era. The Nok Culture" was first identified in 1959 by Bernard Fagg following excavations at the Nok Site in central Nigeria, and stratigraphic analysis placed the culture in the centuries surrounding the birth of Christ. Iron was discovered at the site, and Fagg’s announcement of its unexpectedly early use in West Africa came as a revelation to prehistorians. Before this discovery, the prevailing view was that iron had been introduced relatively late, either through Islamic influence or contact with the Portuguese after 1400. However, subsequent fieldwork revealed furnace remains alongside Nok artifacts, confirming that iron was being smelted locally more than 1,500 years before Portuguese arrival. Remarkably, iron and slag appeared suddenly amid Stone Age remains, unlike the gradual technological progression seen in the Near East. This discontinuity suggests that iron technology was not an indigenous invention in West Africa but rather a product of external influence, likely diffused from the Fertile Crescent. The precise route by which iron-making knowledge reached West Africa, however, remains a subject of ongoing scholarly debate."

beryl, emerald, gems

Studies on the refractive indices and specific gravities of natural and synthetic beryls are reviewed. Effects of impurities, temperature and pressure on these propertles are discussed. For synthetic beryls, refractive indices and specific gravity are strongly affected by the water pressure applied during synthesis. The emerald with refractive indices as high as natural emeralds can be synthesized by using the high pressure technique.

gems

E.J. Gübelin examined black inclusions in about a dozen slabs cut from octahedral diamonds from Ghana to determine their mineral composition and what it might reveal about the origin and cooling history of the host diamonds. The original crystals weighed about 3–4 carats each, and all the slabs strongly absorbed short-wave ultraviolet light, indicating type Ia diamond. The inclusions generally consisted of a central grain surrounded by dark-lined fissures extending along octahedral directions. Gübelin attributed these tension cracks to the difference in thermal expansion between the grain and the diamond and reported that a thin film of pyrrhotite accounted for most of the dark linings. The slabs were ground until the enclosed grains were exposed for electron microprobe analysis. Bright, colorless grains yielded magnesium and silicon, consistent with olivine, while most black grains contained several mineral phases, chiefly sulfides identified as pyrrhotite, pentlandite, and chalcopyrite. One apparently black grain proved to be colorless olivine once its dark coating was removed. In slab D‑1, X-ray maps showed iron and nickel concentrated in the center of a sulfide grain and copper concentrated mainly along its rim. The iron–nickel sulfide phases in two inclusions contained about 7.8% nickel by weight. Gübelin interpreted this unusually high nickel content for a pyrrhotite-like phase as evidence of limited exsolution and suggested that the host diamond had cooled rapidly. The copper-rich phase had the composition of chalcopyrite, though a high-pressure polymorph remained possible. A small silica phase in direct contact with the sulfides also remained uncertain. Overlapping X-ray diffraction patterns prevented a definitive identification, but comparison with published photomicrographs suggested that it might be quartz that had replaced coesite while retaining its form. In slab D‑4, a tiny yellow grain was identified as pyroxene, with its classification as clinopyroxene or orthopyroxene unresolved. On the combined evidence, particularly from slabs D‑1 and D‑4, Gübelin favored an eclogitic origin for the diamonds.

corundum, synthetic corundum.7, Chatham, flux, gems

Groups of Chatham synthetic ruby and blue sapphire crystals are examined to identify features potentially useful for recognizing faceted stones subsequently cut from this material. The specimens comprise four groups of each variety, with individual crystals displaying a tabular or platy habit. Blue colour in the sapphires is unevenly distributed, commonly concentrated towards crystal tips, whereas the rubies appear strongly carmine red when viewed through sufficient depth and pale pinkish red through thinner sections. Surface frosting, bubble-bearing junctions and residual coatings are described but considered unlikely to survive cutting as useful identifying features. Internal characteristics offer greater promise: both varieties contain abundant dark angular platelets, possibly metallic, together with two-phase inclusions, twisted or veil-like feathers and angular growth or colour zoning. The platelets are especially noteworthy for their profusion, although comparable forms can occur in natural ruby. Sapphire spectra show an easily observed absorption band at 450 nm in deeper blue areas, accompanied by much weaker bands at 460 and 471 nm. Thus, unlike conventional Verneuil synthetic blue sapphire, the material can display the familiar sapphire absorption complex. Refractive indices measured on one sapphire surface are normal for corundum, while the ruby absorption spectrum is also conventional. Luminescence provides more distinctive evidence. The synthetic sapphires show patchy yellow fluorescence under long-wave ultraviolet radiation, identified as their most useful diagnostic feature, whereas the rubies exhibit strong red fluorescence and pronounced, persistent phosphorescence after x-ray excitation. Ruby phosphorescence lasted approximately 2–20 minutes following exposures of 10 seconds to 10 minutes. X-rays also induced temporary green or yellow colours in colourless and pale blue sapphire regions; these faded under the heat and light of a tungsten bulb, while deeper blue areas remained unchanged. Isolated colour changes following ultraviolet exposure could not be reproduced consistently. No faceted examples had been examined at the time of writing, so the conclusions remain predictions based on crystal specimens. The author expects combined inclusion and luminescence observations to identify most future faceted material, while recognizing possible difficulties with unusually clean stones and emphasizing caution because x-ray testing can alter sapphire colour.

gems, history of gemology, history of mineralogy, Arabic mineralogy, history of science, crystallography

Recent scholarship has greatly extended our understanding of the history of theories concerning the ultimate nature and structure of matter. This is particularly true for the period preceding the emergence of Dalton’s atomic theory. We now know something of the hierarchical theories of material structure prevalent in the seventeenth century, in the thought of Robert Boyle and Isaac Newton, for example. We have begun to perceive how important Newton’s ideas concerning the structure of matter and the forces that bound substances together or pulled them apart were for the physical and chemical philosophers of the eighteenth century. Dalton’s chemical atomic theory no longer appears quite so lacking in background as it did twenty-five years ago. At the same time, Dalton’s true innovation in turning from consideration of force to consideration of atomic weight has likewise been clarified.

gems, jade, jade imitations, glass

Imitation jades currently circulating in jewellers market under the name of Syberian jade or Reformed jade were investigated by both non-destructive and destructive methods, with special attention to the inclusions. The imitation jades are made of sophisticatedly produced glass, and are dark green, translucent to opaque with glassy, somewhat greasy, luster, have Mohs' hardness of 5-5.5, sp. gr. 2.67 ± 0.02 at 20℃, refractive index 1.523 ± 0.005, and broad absorption spectrum at 4000-4600Å and 6300-7000Å. They contain characteristic inclusions of the following three types; 1) Needle-like inclusions which are identified to be hydroxyl apatite by optical and X-ray investigations, have hexagonal section, and are uniaxial negative, with no pleochroism, higher refractive index than the matrix. These are grouped into three by their length. 2) Dendrite inclusions with 90° braches are identified to be either vapour or liquid phase inclusions, and have lower refractive index than the matrix. 3) Four other types of inclusions, which are not identified. These imitation jades exhibit psudo-optical anisotropy due to apatite inclusions and are easily identified by their inclusions.

quartz, inclusions, gems

Microscopic and freezing-stage observations are used to investigate conspicuous single-phase and two-phase inclusions in a small amethyst crystal, with particular attention to their contents and unusual crystallographic shapes. Numerous negative crystals occur in two parallel arrays beneath prism surfaces and are sufficiently large to be visible without magnification. Some retain conventional quartz-like forms, whereas many are markedly elongated along the host’s horizontal crystallographic axes. Most appear to contain a single fluid or gaseous phase; a smaller number contain liquid and a bubble. The article introduces heating- and freezing-stage microscopy as methods for examining individual inclusions and obtaining information about fluid composition and mineral formation. Heating can establish homogenisation temperatures, although interpretation requires consideration of pressure, and carbon-dioxide-rich inclusions may rupture before homogenisation. Freezing followed by controlled warming permits observation of melting, sublimation and other phase changes that can constrain salinity, gas identity and fluid density. In the amethyst studied, cooling to −155 °C produced solid bodies that subsequently disappeared at −99 °C and −90 °C. Ice in aqueous inclusions melted at −0.4 °C and −0.6 °C, corresponding to reported sodium chloride concentrations of approximately 0.7 and 1.0 wt%, respectively. These observations establish a dilute aqueous component, but the gaseous phase could not be identified conclusively. It did not liquefy even at the lowest temperature reached, and the solid material formed during cooling could not be analysed directly. Methane is considered the most plausible interpretation because the solid’s morphology resembles that observed in methane-bearing inclusions; nitrogen is discussed as an alternative. If methane was present, its behaviour implies trapping at very low pressure. The author also relates the distorted negative-crystal forms to previous observations that methane can influence quartz growth habits and cavity morphology. Comparisons with methane-bearing quartz from the Swiss Alps support this interpretation without removing the uncertainty over gas composition. The coexistence of different inclusion fillings is taken to suggest that the amethyst did not grow in a purely methane environment. Instead, the author proposes that an aqueous solution and supercritical methane coexisted following a rapid reduction in temperature and pressure. The study combines a methodological explanation with a cautiously interpreted case, demonstrating both the information available from inclusion phase changes and the limitations of identification without direct chemical analysis.

chrysoberyl, alexandrite, gems

E.J. Gübelin describes the occurrence, optical properties, and inclusions of alexandrite from the Lake Manyara emerald deposit in Tanzania. The association of alexandrite, emerald, and ruby recalls deposits at Tokowaya in the Urals and Novello in present-day Zimbabwe. X-ray examination identified actinolite as the dominant mineral in the alexandrite host rock, accompanied by enstatite, iron-rich olivine, chondrodite, chrysotile, and dark spinel. Gübelin classifies the host as actinolite schist and relates alexandrite formation to the unusual contact between beryllium-bearing pegmatitic fluids and chromium-bearing rocks. Most specimens showed characteristic trilling, in which three intergrown crystals form a twin assemblage. Some clear pieces could yield faceted gems of up to five carats, although many crystals and fragments were etched, fractured, or heavily included. The material changed from bluish green in daylight to pronounced raspberry red under incandescent light. Representative refractive indices were 1.745, 1.750, and 1.754, with birefringence of 0.008–0.010 and a density of about 3.71 g/cm³. Electron-microprobe analysis of two crystals found chromium and iron, with no detectable vanadium. Gübelin attributes the color change to Cr³⁺ occupying two differently sized octahedral sites in chrysoberyl, whose overlapping absorption bands interact with the differing spectral distributions of daylight and incandescent light. He treats iron chiefly as a modifier of hue and a suppressor of luminescence. The Manyara specimens showed dull red fluorescence under long-wave ultraviolet light, weak yellowish fluorescence under short-wave ultraviolet light, and no response to X-rays. They were opaque to short-wave ultraviolet radiation, as were the natural and flux-grown synthetic comparison stones, while the Czochralski-grown material transmitted it. Inclusions included actinolite fibers, biotite flakes and books, and an apatite crystal in one specimen. Dense actinolite fibers could produce chatoyancy. Partly healed fractures contained liquid-filled tubes and branching channels, and some crystals showed layered or pseudohexagonal color zoning. Despite the strength of the color change in fine specimens, Gübelin expected the supply of gem-quality material to remain scarce and irregular.

diamond, famous gems

Susanne Steinem Patch’s Blue Mystery: The Story of the Hope Diamond (1976) is a carefully researched history of the celebrated blue diamond, tracing its probable origins in India, its association with the French Crown Jewels, its passage through prominent European and American collections, and its eventual donation to the Smithsonian Institution. Patch distinguishes documented events from the numerous legends surrounding the stone, particularly the supposed curse responsible for misfortunes suffered by its owners. The diamond’s earliest probable history begins with Jean-Baptiste Tavernier, the French gem merchant who acquired a blue diamond weighing approximately 112 carats in India, possibly from the Kollur mine in the Golconda region, and sold it to Louis XIV in 1668. Recut in 1673 by the royal diamond cutter Sieur Pitau into a 67⅛-carat stone known as the French Blue, it subsequently became part of the French royal regalia, eventually being incorporated into the elaborate Order of the Golden Fleece alongside the carved red spinel known as the Côte de Bretagne. The French Blue disappeared during the extraordinary theft of the Crown Jewels from the Garde-Meuble in Paris in September 1792. Patch examines evidence that the surviving Hope Diamond was recut from this stolen gem, particularly early nineteenth-century descriptions and drawings establishing its presence in London considerably earlier than generally supposed. Of exceptional historical importance are two drawings dated September 19, 1812, made by John Francillon for diamond merchant Daniel Eliason, whose outlines correspond closely to the present stone. The author traces its subsequent acquisition by Henry Philip Hope, whose remarkable collection included numerous coloured diamonds and the celebrated Hope Pearl, and follows its inheritance by Lord Francis Hope, whose financial difficulties eventually led to its sale in 1901. Subsequent ownership passed through the diamond dealers Simon Franckel, Habib, Rosenau, and Cartier before its acquisition by Evalyn Walsh McLean in 1911–1912. Patch provides detailed accounts of McLean’s extravagant jewellery collection, personal tragedies, and the diamond’s association with American high society. Following her death in 1947, the collection was purchased by Harry Winston, who donated the Hope Diamond to the Smithsonian Institution in 1958. Particularly valuable to gemologists is the discussion of the diamond’s physical characteristics, including its exceptional deep-blue colour, unusual cutting style, and intense orange-red phosphorescence following ultraviolet excitation. Its actual weight of 45.52 metric carats was established when the stone was removed from its mounting and weighed in November 1975, resolving discrepancies arising from historical carat standards. Patch also evaluates the proposed relationship between the Hope and the smaller Brunswick blue diamond, examining the contradictory accounts published by Edwin W. Streeter and the possibility that both originated from the French Blue. The author systematically challenges stories that Tavernier stole the diamond from a Hindu idol, that its owners were inevitably cursed, and that various supposed victims suffered supernatural retribution, demonstrating that many such accounts are unsupported or chronologically impossible. The work combines archival research, contemporary newspaper accounts, historical gem literature, photographs, and documentary illustrations to reconstruct the diamond’s history. Although the principal emphasis is historical, its documentation of provenance, cutting, gemological properties, and the development of one of the world’s most persistent gemstone legends makes it a valuable contribution to diamond literature.

corundum, synthetic corundum.7, assembled stones, gems

Michael O’Donoghue’s Synthetic Gem Materials (1976) is an extensive annotated bibliography of the scientific and gemological literature concerning synthetic gemstones, crystal growth, and related artificial materials. Rather than presenting a conventional textbook on gemstone identification or manufacturing techniques, the work brings together approximately 1,750–2,000 references to published investigations of substances used, or potentially usable, as gemstones. The entries are arranged alphabetically by material, extending from alums to zoisite, and provide information on colour, manufacturers, methods of crystal growth, physical properties, and original literature sources wherever such details are available. The compilation encompasses both historically significant experiments in crystal synthesis and more recent developments relevant to materials entering the jewellery trade during the 1970s. Synthetic ruby receives particularly extensive treatment, with nearly 100 references, reflecting the long history and commercial importance of synthetic corundum. Synthetic spinel and other crystalline materials are also represented, alongside substances developed principally for scientific and industrial applications. An introductory section identifies commercial trade names associated with synthetic gemstones and lists important journals and books containing information on crystal growth and the properties of manufactured materials. The individual records were assembled on reference cards and reproduced in the volume, approximately ten to a page, creating a compact reference tool intended primarily for specialists requiring access to otherwise scattered technical publications. Although primarily concerned with synthetic materials, the bibliography also includes references to gemstone imitations, composite stones, and doublets made entirely from natural materials, thereby extending beyond the strict meaning of its title. Contemporary reviewers noted several inconsistencies in terminology and classification, including the separate listing of beryllia and bromellite, both names for BeO, and differing descriptions of yttrium aluminium garnet (YAG), Y₃Al₅O₁₂. The coverage also extends to certain metals and water-soluble salts of questionable gemological relevance. Other criticisms concerned omissions from the bibliography, notably J.C. Brice’s The Growth of Crystals from Liquids (1973), and the absence of identifiable examples from Djevahiridian, a major European manufacturer of synthetic corundum and spinel. Despite these limitations, contemporary reviews regarded the work as an unusually comprehensive and valuable consolidation of technical literature, particularly because information on synthetic gemstones was dispersed among highly specialized scientific journals and often inaccessible to practicing gemologists. The volume contains few illustrations and is not designed as a practical identification manual, but its annotated references provide a foundation for investigating synthetic gemstone manufacture, material properties, commercial developments, and the history of crystal-growth technology. Published at a time when an increasing variety of synthetic materials was becoming available to the jewellery industry, it represents an important bibliographic resource for gemologists, mineralogists, crystallographers, and researchers concerned with distinguishing natural gemstones from their synthetic counterparts. A contemporary review also noted that supplementary entries were planned for publication in the Journal of Gemmology, extending the usefulness of the bibliography beyond its original publication date.