gems, corundum, treatments.6

Stephan and Müller examine methods for identifying heat treatment in corundum, with particular emphasis on ruby and sapphire. The article reviews the effects of heating on internal features and gemological properties and discusses the diagnostic evidence that can distinguish heated from unheated stones. Microscopic criteria include changes to mineral inclusions, healed fissures, altered growth structures, and other heat-related features, while spectroscopic and analytical methods provide additional evidence where microscopy alone is inconclusive. The authors consider the difficulties created by different heating temperatures, treatment conditions, and starting materials, since some treatments produce conspicuous alteration whereas others leave only subtle indications. The study emphasizes the need to combine microscopic observation with appropriate instrumental methods when determining whether a ruby or sapphire has undergone heat treatment.

gems, corundum, treatments.6

Häger reviews the heat treatment of corundum, explaining the physical and chemical processes by which heating can modify the color and clarity of ruby and sapphire. The article discusses the influence of temperature, atmosphere, and heating conditions on color-producing trace elements and defects in the corundum lattice, as well as the dissolution or alteration of inclusions and other changes affecting transparency. Different treatment objectives and procedures are considered, including the enhancement, removal, or modification of color and the improvement of apparent clarity. The paper provides the scientific background necessary for understanding modern corundum heating and the variables that determine the results obtained from different starting materials and treatment conditions.

gems, antique jewelry, India, jeweled weapons, al-Sabah collection, jade, ruby, spinel

This spectacular collection of nearly 200 jewelled weapons and priceless accoutrements from the Indian subcontinent was assembled over many decades. Produced for aristocratic patrons who valued the arts, these richly decorated edged weapons and other princely objects bear witness to the legendary opulence and refinement of the Indian courts during the sixteenth to the nineteenth centuries. The 9th edition of T&H series on TASC, this is a dazzling celebration of one of the world’s greatest collections of precious weapons. The ninth in Thames & Hudson’s acclaimed series with The al-Sabah Collection, Precious Indian Weapons is divided into fourteen chapters that explore the intricacies and details of hilts, knives, swords, and various other weapons. Rendered in silver, gold, and gems, the dazzling array of decorative motifs presented here includes intricate floral, geometric, and animal designs that testify both to the astonishing skill of their craftsmen and to the area’s complex interconnected cultural histories.

gems, corundum, inclusions.5, E. Billie Hughes, Lotus Gemology

Today women are playing an integral role in the jewellery and gemstone industry from the store front to the laboratory. Here we look at the women who are making a difference.

corundum, color.4, gems

gems, corundum, USA.12, Montana.12, sapphire, Little Belt Mountains, gold, silver

corundum, History.1, gems

gems, corundum, inclusions.5, phenomena, exsolution, stars

Minimization of interfacial energy is the dominant factor governing the equilibrium habit, i.e. orientation and morphology, of a precipitate in the parent crystal. Existing models of optimum interphase boundaries have established criteria that minimize the lattice misfit and/or the strain energy by the comparison of the interplanar spacings of the two interpenetrating lattices. Based on a detailed analytical transmission electron microscopy (TEM) study of two precipitate-matrix systems with different degrees of structural similarity in oxygen sublattices, i.e. hematite in rutile and magnetite in clinopyroxene from metamorphic rocks, it is reported that the optimum interphase boundary and the equilibrium habit of a precipitate in these structurally complex systems can be defined from the special geometry characteristics of diffraction patterns along specific zone axes. Analysis of the TEM results shows that a precipitate in a parent crystal, either with or without a similar oxygen framework, always poses a specific crystallographic relationship with the differences in the g vector pairs ([Delta]g), i.e. misfits of diffraction-spot pairs, of two structures aligned in the same direction, and that the precipitate exhibits a growth habit plane normal to [Delta]g. This new insight into the interfacial energetics, rather than kinetically or topologically controlled mineral growth, can be understood by the coherency of lattice planes in the interphase boundaries and rationalized by the normal-to-[Delta]g principle originally developed for structural transformations in alloys with simple close-packed structures. The normal-to-[Delta]g principle is formulated to calculate the optimum interphase boundaries in the present systems, feldspars and clinopyroxenes of broad geological/mineralogical interest, and gives results comparable to other models yet in a more straightforward manner. This alternative approach can be readily applied in interphase boundary modelling of minerals and sheds light on the growth habit as a potential geothermobarometer of metamorphic rocks.

corundum, Tanzania.12, gems