corundum, Sri Lanka.12, inclusions.5, synthetic corundum.7, gems

This paper describes the identification and crystallographic orientation of the rutile inclusions found in a corundum from the Elahera area, Sri Lanka. The corundum crystals are heavily zoned (fig. 1). The rutile inclusions are almost invariably twinned—either of a needle-like habit with two individuals or geniculated with three or four individuals. The twin plane is {1011} and the needle axis is ⟨011⟩. The orientation of the rutile inclusions in the corundum host is as follows: • Rutile ⟨010⟩ || Corundum [0001] • Rutile ⟨01T⟩ || Corundum ⟨11̅20⟩

corundum, inclusions.5, Thailand.12, gems

gems, olivine, peridot, San Carlos, Arizona, Apache

Each year basalt-topped Peridot Mesa, on the San Carlos Apache Reservation, is a major source for thousands of carats of gem-quality peridot in sizes suitable for use in modern jewelry. Marketed throughout the world, San Carlos material is often confused with, and sold as, peridot from localities that are better known and documented. Peridot Mesa resulted from a single volcanic eruption and basalt flow over an already existing conglomerate base; it is thought to be of late Tertiary or Quaternary age. The peridot is found in irregularly shaped nodules within the basalt. The gemological properties and color range of these Arizona gems suggest an olivine that is rich in the magnesium forsterite end member. Inclusions documented are chromite, chromian spinel, negative crystals, lily pad" cleavages, glass blebs, chrome diopside, biotite, and smoke-like veiling."

jade, jadeite, fei cui, Burma, maw-sit-sit, gems

This article examines both the principles behind the functioning of the scanning electron microscope-energy dispersive spectrometer system and its application to the chemical and structural analyses of gems. The examples presented describe the distinction of natural from treated opals, the relationships observed between a diamond and its kimberlite matrix, the identification of inclusions in ruby and taaffeite, the elemental mapping and chemical analysis of maw-sit-sit,and the study of chemical interrelationships between various types of garnets.

corundum, inclusions.5, gems

The first substantiated identification of corundum (var. ruby) occurring as an inclusion in natural diamond is presented. The ruby is assigned to the eclogitic suite of inclusions in diamond, and the implications of its occurrence are discussed in relation to the genesis of “eclogitic” diamonds. It is concluded that diamond crystallizes from a melt over a long period of time with possible fluctuations in ambient temperature and geochemical environment.

beryl, inclusions, gems

corundum, sapphire, star sapphire, inclusions.5, star quartz, gems

Weibel, Wessicken, Woensdregt, and Wüthrich examine the optical mechanism responsible for chatoyancy and asterism, with particular attention to black star sapphire from southeastern Thailand and milky-white star quartz from Ratnapura, Sri Lanka. They explain that each ray of a star results from light scattering by a set of parallel fibrous structures within the crystal, with refraction at the curved cabochon surface also contributing to the observed effect. Contrary to the usual explanation involving rutile silk, electron microscopy revealed no inclusions in the Thai black star sapphire; its fracture surfaces instead show stepped structures with trigonal dislocations, and the authors suggest regular lattice dislocations or twinning as possible causes of the asterism. In the Ratnapura star quartz, electron diffraction identifies the scattering needles as sillimanite, averaging about 0.02 μm thick, rather than rutile; their imperfect orientation accounts for the diffuse and incomplete star.

synthetic beryl, emerald, gems

As-grown and faceted crystals of synthetic hydrothermal emeralds from the USA and USSR were compared in terms of morphology, internal features, and physical properties. The USSR emeralds are notably closer to natural emeralds in physical and optical properties, although both types differ from natural stones primarily in their internal features. USA emeralds (SG: 2.67–2.68, RI: ω 1.572–1.574, ε 1.568–1.569) display bright red fluorescence under 365 nm UV, show Chelsea filter reactions (red), and often contain optical strain, “earthworm” cracks, phenacite, and 2- or 3-phase inclusions—often originating from natural beryl seed plates. USSR emeralds (SG: 2.70–2.71, RI: ω 1.583–1.586, ε 1.577–1.579) are slightly softer (H 7–7.5), show weaker UV fluorescence and pleochroism closer to natural emeralds, and lack spikes or strong zonation. Their inclusions include more naturalistic features like “wheat-head” textures, 2- and 3-phase inclusions, and reddish-brown plates. Growth habits differ slightly, with the USSR stones typically showing multiple growth planes ({112̅1} and {112̅0}) and shorter estimated growth times. Overall, USSR hydrothermal emeralds reach ~90% similarity to natural emeralds, versus ~80% for USA stones and 40–60% for flux-grown emeralds.

corundum, quality.10, gems

A practical guide to buying, selling, evaluating, and investing in precious gemstones, written by New York gem dealer Benjamin Zucker. Originally published in 1976 as How to Invest in Gems, this revised second edition reflects the dramatic increases in gemstone prices during the late 1970s and advocates fine rubies, sapphires, emeralds, and diamonds as long-term investments and hedges against inflation and currency depreciation. Individual chapters examine the geological occurrence, mining, cutting, identification, quality factors, geographical origins, and market values of the four principal gemstones, with particular attention to color, clarity, size, and inclusions. Ruby sources discussed include Burma, Sri Lanka, Thailand, Cambodia, Afghanistan, and Kenya; sapphire sources include Kashmir, Burma, Sri Lanka, Thailand, Australia, and Montana; and emerald sources include Colombia, Brazil, Rhodesia, Zambia, Afghanistan, and others. Zucker describes methods of distinguishing natural from synthetic gemstones using microscopy, refractive index measurements, ultraviolet fluorescence, and characteristic inclusions, drawing upon the research of Eduard Gübelin and other gemologists. A substantial section examines the history and operations of De Beers, including its control of diamond production and distribution, relationships with Soviet producers, and methods of stabilizing diamond prices. Other chapters address gem appraisals, auctions, retail and wholesale pricing, and the investment potential of tourmaline, garnet, aquamarine, and other gemstones. Suggested investment portfolios range from $10,000 to $1 million, with recommendations concerning gemstone varieties, sizes, and qualities. Appendices provide comparative gemstone prices from 1968 to 1979, descriptions of major museum collections, an overview of gemological institutions and grading systems, and historical accounts of jewelry craftsmanship, Fabergé, Marco Polo, and Louis XIV. Particularly interesting are the author's firsthand account of purchasing a 94 ct blue star sapphire subsequently exhibited at the American Museum of Natural History and his descriptions of the Iranian Crown Jewels. Illustrated with numerous color and black-and-white photographs of gemstones, inclusions, mining operations, jewelry, and museum treasures, the book offers a revealing contemporary perspective on the international gemstone trade and investment philosophy of the late 1970s, although its price information and some gemological interpretations are now dated.

amber, inclusions, gems