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

One of the beauties of working with gemstones is that each time you peer into a stone, you get a glimpse of the universe held within. When we first examined the scene in a star sapphire (see above), we were delighted with the view. A feature that immediately stands out is the triangular crystal, which displays terraced growth features and iridescence on the surface when illuminated with a fiber-optic light. Analysis with micro Raman revealed that this crystal is apatite. What makes the scene even more stunning is the way the crystal seems to float over a cloud of rutile silk. This same silk is what creates asterism in the stone. While in this case the apatite crystal resides in a sapphire from Sri Lanka, apatite has also been reported in corundum from a variety of sources, including Afghanistan, Cambodia, Madagascar, Myanmar, Nigeria, Pakistan, Tanzania, Thailand, the United States, and Vietnam. Apatite can be found not only in ruby and sapphire from different origins, but also in many other types of gems. In our laboratory, we have encountered apatite inclusions in emerald, spinel, and garnet. Apatite is a relatively common mineral, so it is not surprising to find it so often as an inclusion. Although it may occur frequently, in this instance it is anything but mundane.

gems, corundum, Thailand.12, treatments.6

A large black star sapphire was brought in for testing. Two large pits on the base were carefully filled with brown dopping varnish. After removal of the varnish with alcohol, it was found that a large portion of the base had been filled with a lead glass.

gems, gemology, ruby, sapphire, jade, inclusions.5, corundum, garnet, quartz, China, Tibet, Thailand, Burma, Myanmar, Sri Lanka, Inner Mongolia, India, Madagascar, Mozambique, Tanzania, Rwanda, East Africa, Greenland

From the dawn of time, precious stones have both attracted and fascinated humans in ways that few other items could. For 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. This book presents a completely fresh approach to the subject. Dubbing it humanistic gemology, the authors take readers around the world, showing the places they have explored in their search for gems, along with the people and cultures encountered along the way. Within this volume, remarkable photographs of the human world are interwoven with images of the microscopic realm of the gems themselves. In a lifetime beset by time control, where living is broken into ever smaller bits, as you browse through these pages suddenly you plunge into a domain of frozen time, one that affords vistas of millions or even billions of years. For jewels offer not just superficial beauty, but a window on the primordial forces that birthed both our planet and universe. Inside Out – Gemology Through Lotus-Colored Glasses represents a fascinating new direction for gemology, linking the external and internal worlds of precious stones for the first time.

gems, beryl, emerald, emerald fillers, LW UV torch

Of the treatments we see in the laboratory, fissure filling has become one of the most ubiquitous. We have observed this treatment in a variety of stones, including emerald, ruby, sapphire, spinel, tourmaline, tanzanite, and more. The filling of fractures minimizes their appearance, making the gems appear cleaner. Fissure filling can be detected with a variety of methods. One way is to examine the infrared spectrum, where some fillers display distinctive peaks. Another is the hot point method, where oils can be observed leaking out in droplets. Some fillers are unmasked with simple observation in the microscope, because they display flashes of color or because they include visible dyes.

gems, corundum, ruby, sapphire, books

A discussion of the literature of ruby and sapphire (corundum), with particular emphasis on the most collectible books covering ruby and sapphire around the world.

gems, spinel, inclusions, Burma, Mogok

Lotus Gemology in Bangkok received a large parcel of dark red spinels for identification. Their colors, inclusion features, and trace element chemistry suggested that they originated from Myanmar’s Mogok Stone Tract. In one faceted specimen, a crystal was found breaking the surface. The crystal’s surface luster suggested a refractive index below that of the host spinel, and undercutting suggested it was also significantly lower in hardness. The inclusion’s interior also displayed signs of cleavage. Thinking it was possibly a carbonate, we proceeded to do micro-Raman analysis on the crystal. To our surprise, the result was fluorophlogopite. Fluorophlogopite, KMg₃(AlSi₃O₁₀)(F,OH)₂, is a species in the mica group and a member of the trioctahedral mica subgroup. To the best of our knowledge, this is the first reported instance of this species in spinel. Nor are we aware of it having been found included in any gem mineral to date.

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, corundum, treatments.6, sapphire, pressure treatment, heat treatment

Sapphires heated with pressure reportedly entered the trade already about 10 years ago (Hughes et al., 2019), although in rather small quantities. Described by several gemological articles in the past few years (Choi et al. 2014a, 2014b, Song et al. 2015, Leelawatanasuk et al. 2016, Choi et al. 2018), this new variation of heat treatment came into the spotlight only recently, based on claims that sapphires heated with pressure have a stability issue (Peretti et al. 2018 and 2019). As a consequence, there have been extensive discussions about this topic among gem laboratories and within the gem trade, resulting in several press releases (e.g. LMHC 2018) and statements (AGTA 2018). The following article is mainly based on a presentation (pdf file of presentation, LMHC 2019) given at the GILC Conference (www.gemstone.org/events/gilc) in Tucson 2019 summarizing the results of a joint research project and extensive discussion between the following laboratories and entities (in alphabetical order): CGL Central Gem Lab, Japan; CISGEM, Italy; German Gem Lab (DSEF), Germany; Dunaigre Consulting, Switzerland; Gemological Institute of America (GIA), USA; Gem and Jewelry Institute of Thailand (GIT); GJEPC-GTL, India; Gübelin Gem Lab, Switzerland; Hanmi Lab, South Korea; ICA GemLab, Thailand; Lotus Gemology, Thailand; Swiss Gemmological Institute (SSEF), Switzerland.

gems, corundum, Madagascar.12, inclusions.5