corundum, inclusions.5, diamond, beryl, emerald, spectroscopy, gems

Dele-Dubois, Dhamelincourt, and Schubnel examine the application of Raman spectroscopy to the non-destructive identification of mineral inclusions in diamonds, sapphires, and emeralds. The technique permits inclusions to be analyzed in situ through the host gemstone by means of their characteristic Raman spectra, avoiding the need to extract or otherwise damage them. The authors demonstrate the usefulness of Raman spectroscopy for identifying very small inclusions that may be difficult to determine by conventional microscopy, illustrating its value both for gemological identification and for investigating the mineral assemblages trapped during gemstone formation.

diamond, inclusions, gems

Gübelin reviews the nature and significance of mineral inclusions in natural diamond, considering included minerals as evidence bearing on diamond formation and its geological environment. The paper surveys the principal types of mineral inclusions recognized in diamonds and discusses their mineralogical relationships and importance for understanding the conditions and processes of diamond genesis.

diamond, inclusions, gems

Gübelin discusses black inclusions occurring in diamonds and their appearance under gemological examination. The article concerns the nature and identification of these dark internal features and their significance as inclusions in natural diamond.

corundum, fashioning.9, cutting, properties.3, gems

First published in 1972, Descriptions of Gem Materials brings together concise accounts of materials used in faceting and cabochon cutting, linking mineral identification with practical assessment of cutting behaviour. Glenn and Martha Vargas adopt an inclusive definition of gem material, covering familiar jewellery stones, uncommon collector minerals, ornamental rocks and manufactured products. The original edition described slightly more than 250 materials; the revised third edition expands this coverage to more than 550. Entries follow a consistent arrangement, separating physical properties from optical characteristics so that specimens can be compared readily. Data include chemical composition and formula, crystal system and habit, hardness, specific gravity, cleavage, fracture, streak and characteristic inclusions. Optical descriptions cover colour, refractive index, critical angle, birefringence, pleochroism, dispersion, transparency, lustre, optic character and, where applicable, the angle between optic axes. Pronunciation guides, name derivations, varieties, synonyms and misleading trade names assist readers in navigating gemstone terminology. Short commentaries connect these properties with the availability and suitability of rough, identifying promising sources and difficulties such as brittleness, cleavage, inclusions, softness or poor polishing response. The authors recognise that rarity alone may justify cutting a specimen for a collection, even when it lacks the durability or appearance expected of conventional jewellery gems. Natural materials and manufactured products occupy separate sections, with synthetic counterparts distinguished from products having no natural equivalent. The latter section also introduces production methods and the use of colouring additives. Identification tables arrange materials by increasing hardness, specific gravity and refractive index, allowing measured properties to narrow the possible identity of an unknown specimen. Introductory explanations and crystal drawings establish the terminology used throughout, while a glossary, an index of alternative and incorrect names, and a selected bibliography support consultation. The descriptions emphasise usual properties and acknowledge that uncommon variations require fuller mineralogical or gemmological references. Combining tabulated information with observations from cutting, teaching and consultation with specialists, the work serves as a practical bridge between descriptive gemmology and the handling of rough material.

inclusions, gems

inclusions, gems

First comprehensive article on the determination of inclusions in gemstones by means of the electron microprobe. Techniques are described and results explained. Fine color illustrations. Essentially the same article appeared in Journal of Gemmology, 11(5), 1969, pp. 149–192, with 80 color photographs, 3 figures, and 49 references.

jade, jadeite, fei cui, nephrite, Wyoming, Burma, inlusions, gems

ekanite, gems

Gübelin gives a detailed gemological account of ekanite, a newly recognized metamict gem mineral from Ceylon, named for F. L. D. Ekanayake, who first recognized its unusual character. The material occurs in the gem gravels near Ellawala, northeast of Ratnapura, and is typically greenish-brown to yellowish-green, transparent to translucent, and sometimes displays chatoyancy or asterism caused by oriented clouds of minute inclusions. Gübelin describes its gemological properties, including its singly refractive character, refractive index of about 1.595, specific gravity of about 3.28, and weak absorption bands, together with microscopic features and inclusions. Chemical investigation showed calcium, thorium, silicon, aluminium, and lead, while measurements demonstrated significant radioactivity associated particularly with thorium. The destruction of the original crystal lattice through radioactive decay accounts for its metamict condition. Gübelin also discusses its probable original crystalline state, chemical composition, and age as estimated by thorium-lead dating, establishing ekanite as an unusual new addition to the gem minerals of Ceylon.

corundum, synthetic corundum.7, gems

Describes ruby specimens consisting largely of natural cores covered by thin synthetic layers, reportedly grown hydrothermally. Their physical constants match natural ruby, and inclusions within the cores can make identification misleading. Minute gas bubbles in the coating and a sharp boundary between core and overgrowth reveal their composite nature; the observed features suggest growth from a melt rather than a hydrothermal process.

corundum, Brazil.12, gems

Describes sapphire crystals from the Coxim River area of Mato Grosso, Brazil, noting unusual rounded inclusions resembling the gas bubbles commonly associated with synthetic corundum.