gems, instruments, beryl, emerald treatments, inclusions

As laboratory gemmologists, we are frequently asked by friends and colleagues for recommendations on lab equipment. Often the focus is based around the most modern and advanced instrumentation, much of which is out of reach for what my grandfather likes to call the “great unwashed.” One piece of equipment that is often overlooked is the humble ultraviolet (UV) lamp. Although it is an older and relatively affordable tool, it is an essential test in our laboratory, and we examine all submitted stones under UV light. Often used in diamond testing, it can also be a tremendous help with coloured gems, in detecting treatments and synthetics, as well as a capable tool to screen pieces of jewellery with many smaller stones.

gems, corundum, ruby, Madagascar.12, inclusions.5

We have examined thousands of rubies in Lotus Gemology’s laboratory, yet the hours spent peering into the microscope are never mundane because each stone captures its own piece of history through its inclusions. Recently a client submitted one such gem for testing, a 3.04 ct specimen measuring 11.98 × 7.13 × 4.21 mm that was identified as an untreated ruby from Madagascar based on inclusions. In the microscope, a few bright brownish red crystal inclusions immediately stood out. They were transparent, with a saturated red hue that, in darkfield illumination, was conspicuous even against their ruby-red background. Some were also cut through on the surface, allowing us to view them with reflected light. Observation of the surface showed that the crystals had a luster just slightly lower than that of the surrounding corundum, suggesting a slightly lower RI. To get a better idea of the crystals’ identity, we examined them using micro-Raman spectroscopy with a WITec Alpha 300R Raman imaging system with a 532 nm laser, which identified them as staurolite. Staurolite, Fe₂Al₉Si₄O₂₂(OH)₂, is a red to brown mineral known to occur in Madagascar. Its RI values are nα = 1.736–1.747, nβ = 1.740–1.754, and nγ = 1.745–1.762. Corundum has a slightly higher RI range, with nₒ = 1.767–1.722 and nₑ = 1.759–1.763. The combination of microscopic observation and Raman spectroscopy gave us confidence that these were indeed staurolite crystals. It is no wonder these crystals initially stood out. To the best of our knowledge, this is the first recorded observation of staurolite as an inclusion in corundum. This Madagascar ruby has encapsulated a fascinating kernel of history within its depths.

gems, spinel, inclusions

To the jeweler, spinel is famous for its vivid colors. But for the gemologist, this gem is unlike any other. Its extreme hardness allows a fine polish. Couple this with single refraction, which eliminates the image blurring found in most other gems, and a varied landscape of inclusion subjects, and the result is an unparalleled canvas of delight for the photomicrographic artist.

gems, corundum, Madagascar.12, inclusions

A look at sapphire in southern Madagascar, including a description of its inclusions.

gems, corundum, inclusions.5

In a new series for Gems&Jewellery magazine, Bangkok-based gem testing lab Lotus Gemology delves into its photomicrograph archive, Hyperion, to help gemmologists tackle tricky inclusions. In this inaugural column, we discover the difference between crystal types in ruby and sapphire.

gems, corundum, inclusions.5, Burma.12

In the third of a four part series for Gems&Jewellery, Bangkok-based gem testing lab, Lotus Gemology, shares pairs of photographs that, when placed side-by-side, reveal the full story of an inclusion or treatment. In this issue, we explore how inclusions can help to reveal the origin of rubies...

gems, corundum, sapphire, inclusions.5, Madagascar.12

Growth tubes are a typical inclusion in corundum and often seen during examination in the laboratory. While commonplace, a stunning cluster such as the one seen above calls out to the photomicrographer. At the surface these tubes are cut through and some black debris has become lodged inside the ends, while deeper within the stone they still display a fiery glow, reminiscent of rockets launching into the sky. Not only do these tubes spark the imagination, but they can actually tell us a lot about the identity of their sapphire host. The limonitic staining found deeper in the tubes is a yellowish orange, suggesting that they have not been altered by heat treatment. These stains often turn a darker reddish or brownish color in heat-treated stones (J.I. Koivula, “Useful visual clue indicating corundum heat treatment,” Fall 2013 G&G, pp. 160–161). Furthermore, we have observed in the past several months that these prominent growth tubes are a common feature in Madagascar sapphire. While the tubes can be found in corundum from other origins, they seem particularly common in the Madagascar material that has been entering the Bangkok market in greater numbers recently. When taken into account along with other features, they provide a clue to the origin of these sapphires. Thus, what initially appeared to be a mundane inclusion is both visually impressive and gemologically significant, as it provides hints to the origins and treatments of corundum.

gems, corundum, sapphire, Burma.12

Gems are renowned for their outward beauty, but their in-ternal world can be just as striking. Lotus Gemology re-cently came across a Burmese sapphire, cut as a cabochon and measuring 8.92 × 7.10 × 4.75 mm, that displayed a six-rayed star. Once we examined it under the microscope, we were surprised to find that this celestial theme carried through to the inclusion scene inside (figure 13).

corundum, History.1, Chemistry.2, properties.3, color.4, inclusions.5, treatments.6, synthetic corundum.7, assembled stones.8, fashioning.9, quality.10, geology.11, sources.12, Australia.12, Afghanistan.12, China.12, India.12, France.12, Laos.12, Madagascar.12, Mozambique.12, Malawi.12, Myanmar.12, Pakistan.12, Sri Lanka.12, Tanzania.12, Tajikistan.12, Thailand.12, Vietnam.12, USA.12, Montana.12, gems, irradiation paper on ruby, Indian lapidary, color science, Kashmir, Mogok

From the dawn of time, ruby and sapphire have both attracted and fascinated humans in ways that few other items could. While objects of desire are found throughout the natural world, physical beauty is too often ephemeral. From the allure of a man, woman, flower or butterfly, through the fleeting moments of a sunset, there is little that lasts and practically nothing that can be passed down to our descendants. The exception is precious stones. Not only are they the most durable creations of mother nature, but their visual splendor is truly eternal. In this companion to his 2013 book, Ruby & Sapphire—A Collector’s Guide, Richard Hughes examines these gems from the gemological standpoint, delving into them not just from the aesthetic, but also from the scientific point of view. The product of nearly 40 years of firsthand experience, this book covers the subject from A–Z. History, sources, prices, quality analysis, causes of color, geology, synthetics and treatments—everything is here. Ruby & Sapphire—A Gemologist’s Guide arguably represents the most comprehensive volume ever written on a single precious stone. With over 1000 photos, maps and illustrations and 3500 references, it is nothing less than a tour de force of gemological scholarship.

gems, corundum, inclusions.5, Burma.12

Project to identify inclusions in ruby from Mogok, Myanmar