corundum, color.4, gems

The expanding role of recording spectrophotometers in gem identification is illustrated through the development of the Gem Testing Laboratory of Great Britain’s equipment and several diagnostic case studies. Although the hand-held spectroscope remains valuable, its limitations become significant when precise wavelength measurements, absorption-band shapes, or information outside the visible region are needed to distinguish synthetic gems and treated natural material. Diamond absorption features provide an example: the H3 zero-phonon line at 503.2 nm and the H4 line at 496 nm require careful distinction because an H3 phonon sideband can be mistaken for the latter, potentially affecting interpretation of color origin. Cooling diamonds to approximately 120 K improves visual resolution, but recording instruments provide more complete spectral information. The laboratory initially acquired a Pye Unicam PU 8800 ultraviolet-visible spectrophotometer and subsequently added a Nicolet 510 Fourier-transform infrared spectrometer as infrared analysis became increasingly important. Guidance is given on interpreting absorbance and transmittance curves and relating recorded features to observations through a hand spectroscope. Examination of De Beers synthetic yellow to greenish yellow and brownish yellow diamonds combines ultraviolet luminescence, growth-sector zoning, metallic and dust-like inclusions, and infrared spectra. The examined synthetic stones show isolated-nitrogen absorption characteristic of type Ib diamond without aggregated-nitrogen features, whereas a natural yellow type Ib comparison stone also contains an aggregated-nitrogen peak. Infrared spectroscopy also identifies amber in mounted earclips and beneath artificial coatings on beads when conventional tests are restricted by mounting or surface treatment. The earclips display colored outer layers surrounding colorless interiors, consistent with heat treatment; the beads have an additional orange artificial coating over a yellow surface layer. A further case concerns a 5.80 ct diamond whose appearance varies among green, gray, and brown under different lighting. Its visible spectrum does not fit a straightforward conventional category. Strong blue-green phosphorescence following short-wave ultraviolet exposure and electrical conductivity suggest type IIb diamond, and comparison of its infrared spectrum with recorded reference spectra confirms that classification despite its atypical color. These examples demonstrate how instrumental spectroscopy complements microscopy and routine gemological observations, providing decisive information in cases where appearance or simpler tests are insufficient. The article argues that increasing identification challenges justify advanced instrumentation and that clearly presented spectral curves remain accessible and useful to practicing gemologists.

corundum, Inclusions.5, Burma.12, gems

inclusions, photomicrography, gems

De Goutière presents a brief photographic essay celebrating the visual interest of gemstone inclusions through three colour photomicrographs of two specimens. The emphasis is on the striking patterns revealed by microscopic observation and their resemblance to recognizable scenes or abstract compositions. The first photograph shows a thin film within a light green beryl crystal that has been ground to a thickness of 1 mm. Its intricate, multicoloured forms are likened to a tropical garden containing a palm tree and butterflies. Branching and fan-like details occupy a broad field of yellow, blue, green, and violet, with darker areas framing the composition. The comparison concerns the appearance of the photographed inclusion rather than the presence of biological material. The remaining two photographs depict unusual tubular inclusions in a 0.07 ct round brilliant-cut diamond. In one view, bright, angular, tube-like forms appear among the stone’s reflected facet patterns and several dark rounded features. The accompanying caption humorously compares their extraordinary configuration to uncontrolled laser drilling. A second photograph presents a pavilion view of the same diamond, revealing the network from another direction. Here the tubes form a conspicuous labyrinth of straight segments and sharp changes in direction against contrasting bright and dark areas. De Goutière characterizes the effect as natural abstract art, using the change of viewpoint to present a different composition within the same small gemstone. The editorial introduction places these photographs within an ongoing presentation of the author’s work with camera and microscope and frames the specimens as subjects created by nature. The contribution is descriptive and pictorial: it provides the host materials, the preparation thickness of the beryl, and the weight and cut of the diamond, but does not identify the thin film’s composition, explain the tubular inclusions’ formation, or supply magnification and illumination details. Its central purpose is to demonstrate the aesthetic possibilities of inclusions and the distinctive internal images that gem photomicrography can reveal.

gems

Backler criticizes inadequately researched jewellery valuations and sets out the knowledge, documentation, equipment, and ethical standards required for a defensible professional appraisal. She treats the valuation report as a legal document that must describe the object fully, substantiate its conclusions, and communicate clearly to both specialists and clients. Insurance valuations are distinguished from probate assessments: the former concern current replacement on a like-for-like basis, while the latter are described as assessments based on material values without workmanship, taxes, or commercial mark-ups. Reliable practice requires gemmological training, continuing education, suitable testing instruments, reference literature, current diamond and coloured-stone prices, and familiarity with precious-metal testing and markets. Appraisers must also understand exchange rates, inflation, import duties, taxation, labour costs, and the successive mark-ups affecting retail replacement. Detailed worksheets and retained records provide the evidence needed to explain conclusions, resolve later disputes, and support testimony in court. Backler condemns valuations altered to accommodate clients’ wishes and deliberate undervaluation intended to discredit competitors or secure goods cheaply. She emphasizes the client’s dependence on professional honesty and the obligation to disclose gemstone treatments, including oiling, glass filling, laser drilling, dyeing, impregnation, heating, and irradiation. Poor valuations can leave clients seriously underinsured, while incomplete descriptions impede identification and encourage disputes over alleged stone substitution. She recommends examination in the client’s presence where practicable and warns that cleaning can markedly change a jewel’s appearance. A case study contrasts a brief, inaccurate retail appraisal with a detailed replacement assessment of a diamond engagement ring and matching wedding band. The deficient report underestimated the principal diamond’s weight, assigned a substantially lower clarity grade, and was followed by an offer to purchase it cheaply. The fuller assessment records metal fineness and weight, construction, gemstone measurements, estimated weights, colour, clarity, fluorescence, finish, identifying marks, and condition. Editorial annotations by R.W. Hughes qualify several of Backler’s assertions. They stress that some treatments are difficult or impossible to detect, that observing an appraisal may introduce security problems and pressure to rush, and that distinctive inclusions or surface features can help establish identity before cleaning. The concluding editorial also cautions against condemning all retail appraisers and emphasizes specialization, practical experience, and candid acknowledgement of uncertainty. Both author and editor ultimately argue that trustworthy valuation depends on documented evidence, sustained professional competence, integrity, and recognition of the limits of one’s expertise.

corundum, quality.10, synthetic corundum.7, gems

corundum, history.1, gems, Arabic mineralogy, ancient gemology, history of gemology, antique gems, glyptic, technology, analytical, classical world

gems, Ceylon, Sri Lanka, ekanite, metamict

Gauthier and Fumey examine ekanite as an unusual metamict gemstone, discussing the structural damage produced by its natural radioactivity and the resulting effects on its gemological properties. They describe the stone’s appearance and physical and optical characteristics and consider the difficulties that metamictization creates for conventional mineral identification. The study emphasizes the relationship between ekanite’s thorium-bearing composition, internal irradiation, and progressive destruction of its original crystalline structure, making the mineral an instructive example of a naturally metamict gem material.

gems, chrysoberyl, alexandrite, synthetic alexandrite, crystal growth, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), Tairus, Kyocera, flux growth, Czochralski, zone melting

Infrared spectroscopy provides a means to distinguish natural from synthetic alexandrites in the range 2000–4200 cm⁻¹, as determined by a study of spectra obtained from 15 natural and 28 synthetic alexandrites from a variety of sources. The technique is nondestructive and, with Fourier transform instrumentation, extremely rapid. It is especially useful for identifying stones that contain no distinguishing inclusions.

gems, garnet, color-change garnet, East Africa

Over the past 18 months, four exceptional change-of-color garnets from East Africa have been observed, notable for exhibiting a striking color shift similar to that of fine Russian alexandrite—green in daylight or fluorescent light and red under incandescent light. While East African color-change garnets have been known for years, most are either too dark or lack a dramatic shift, particularly when cut. GIA’s Research Department examined three of these remarkable stones, which showed refractive indices of 1.770 and 1.763. Spectroscopic analysis using a Beck prism spectroscope and a Pye Unicam UV-visible dual-beam spectrophotometer confirmed the presence of absorption features typical of pyrope-spessartine garnets. Semiquantitative chemical analysis via energy dispersive X-ray fluorescence (EDXRF) revealed compositions consistent with pyrope-spessartine garnets containing relatively high manganese levels. Interestingly, only a trace amount of chromium (0.1 wt.% Cr₂O₃) was detected, while the vivid color change was attributed almost entirely to more than 1 wt.% V₂O₃ (vanadium oxide) present in each sample.

gems, garnet

Pyrope garnets occur in near-colorless to light orange and pink, as well as the familiar red. Because the pale-hued pyropes are unfamiliar to gemologists, their low refractive index usually results in their misidentification as grossular. This note clarifies the means by which these unusual garnets, predominantly from East Africa, can be properly and easily identified with a refractometer and a spectroscope.