Enwave Optronics, Inc.

Small “Surprise” in Elbaite Tourmaline
Recently, a 0.86 ct orange-yellow elbaite tourmaline cabochon was submitted to Taiwan Union Lab of Gem Research (TULAB) for identification service. The stone contained many prismatic and round xenocrysts. Among these inclusions were a prismatic crystal associated with a round crystals were observed near each other, a composition resembling an exclamation point (figure 1). The crystals were later confirmed to be diopside using Raman spectroscopy. Darkfield illumination, plane polarized light, and extended depth of field were adopted to obtain a clear microscopic image of this little “surprise” inside the gemstone.

Figure 2. The “exclamation point” inclusions were identified as diopside crystals using Raman spectroscopy. Photomicrograph by Shu-Hong Lin; field of view 4.11 mm.

Shu-Hong Lin
Institute of Earth Sciences, National Taiwan Ocean University
Taiwan Union Lab of Gem Research, Taipei
Tsung-Ying Yang, Kai-Yun Huang and Yu-Shan Chou
Taiwan Union Lab of Gem Research, Taipei

Gems & Gemology, Fall 2022, Vol. 58, No. 3, P. 364-365.

A Zircon with Strong Photochromic Effect

Recently, a 6.54 ct oval faceted gemstone with greenish blue color (figure 1, left) was sent to Taiwan Union Lab of Gem Research (TULAB) for identification. The specific gravity of this stone was 4.68, and the refractive index was over the limit of the refractometer. Microscopic observation showed strong birefringence. In addition to standard gemological testing, Raman spectroscopy and comparison with the zircon reference spectrum R050203 from the RRUFF database (figure 2) confirmed it was a zircon. It was particularly worth noting that this zircon showed a significant color change from greenish blue to very dark yellowish green (figure 1) when exposed to a long-wave ultraviolet lamp.

To determine the extent of the color change and whether it was permanent or reversible, the zircon was first exposed to long-wave UV light for one minute and then under 10W white LED light for another minute (the light sources were placed approximately 3 cm away from the gemstone). After repeating this process several times with each exposure one minute longer than the previous time, we confirmed that the color changed from medium light greenish blue with strong saturation to a medium dark greenish yellow with lower saturation after two minutes of long-wave UV light exposure. However, the greenish yellow color gradually returned to the stable greenish blue color after photobleaching with LED white light for 30 minutes. Therefore, the stone was a photochromic zircon with reversible color change (as reported in N.D. Renfro, “Reversible color modification of blue zircon by long-wave ultraviolet radiation,” Fall 2016 G&G, pp. 246–251). After the color change reached its full extent under long-wave UV light, the zircon was analyzed by visible spectroscopy to record its continuous spectral change during the photobleaching process every six minutes (figure 3). The resulting spectra revealed that the light transmittance in the range between 450 nm and 550 nm gradually increased during the photobleaching process, and the greenish blue color finally returned to a stable state after 30 minutes.

Although this type of photochromic zircon has previously been reported, a zircon over 6 ct with such a significant photochromic effect is still rare and worth noting, especially since it exhibited a distinct difference in hue, tone, and saturation.

Figure 1. This 6.54 ct zircon showed a significant color change from medium light greenish blue (left) to very dark yellowish green (right) after exposure to long-wave UV for two minutes, and the color was reversible during the photobleaching process with LED white light. Photos by Kai-Yun Huang.
Figure 2. The stacked Raman spectra of the greenish blue zircon and a zircon reference spectrum from the RRUFF database; spectra are normalized and baseline-corrected.
Figure 3. Visible spectra of the zircon (after UV light exposure) during the photobleaching process were recorded every six minutes. The gradually decreasing spectral change implied that the color tended to stabilize.

ABOUT THE AUTHORS
Shu-Hong Lin is chief gemologist, and Yu-Shan Chou and Kai-Yun Huang are gemologists, at Taiwan Union Lab of Gem Research in Taipei.

://www.gia.edu/gems-gemology/summer-2022-gemnews-zircon-photochromic-effect

“Boomerang” Inclusion in a Rough Topaz
https://www.gia.edu/gems-gemology/summer-2022-microworld-boomerang-inclusion-rough-topaz

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Fishbone Inclusion in a Burmese Peridot from Mogok
Recently, an 83.25 ct cushion faceted peridot with medium dark yellowish green color and good clarity (figure 1) was sent to the Taiwan Union Lab of Gem Research (TULAB) for identification service. This peridot from Mogok, Myanmar, was relatively rare in the Taiwan market because of its impressive size, color, and clarity. Microscopic examination revealed a few short needle inclusions and a fishbone-shaped inclusion (figure 2), the latter of which is common in peridot from this origin. The backbone appeared to be a long-prismatic crystal with some vertical cleavage planes along it, while the smaller branches were composed of parallel tabular inclusions which might result from epitaxial exsolution. Due to peridot’s strong birefringence, bright-field illumination and plane polarized light were adopted to reduce the interference and obtain clear microscopic images.
Shu-Hong Lin
Institute of Earth Sciences, National Taiwan Ocean University
Taiwan Union Lab of Gem Research, Taipei
Figure 15. The fishbone-like inclusion in the Burmese peridot. Photomicrograph by Shu-Hong Lin; field of view 1.32 mm.

This article was published on Gems & Gemology, Spring 2022, Vol. 58, No. 1, p6
Please refer to the link below for the pdf file of the journal：https://www.gia.edu/doc/spring-2022-gems-gemology.pdf
PS: The additional photo is a front view of the peridot

Tektite or obsidian? Natural glasses from Indonesia, Arizona, USA or Colombia.
Photo/ Text by TULAB of GEM RESEARCH.

In recent years, a lot of granular natural glass claimed to be "tektite" appeared on the market, which might be identified as "tektite" with certificates issued by the gem labs in China, Taiwan and Hong Kong. Most of the sellers use the trade names as Indonesian tektite, Saffordite, Colombian tektite or Mexican tektite. At the beginning, such objects were submitted to the TULAB for identification. Our gemologists confirmed that these objects were granular obsidian by various advanced instruments (FTIR, Micro-Raman, EDXRF, UV-Vis). However, some sellers still claimed that those natural glasses were tektite.

Therefore, about two years ago, TULAB started a series of tektite research, and successively collected obsidian samples from different origins and tektite samples from different origins, totaling more than 300 pieces of samples. After EDXRF analysis, traditional gemological testing, micro-Raman analysis, FTIR analysis, and UV-Vis analysis, it was finally concluded that the aforementioned "granular natural glass" were all obsidian, and a lot of obsidian from Indonesia in the market was claimed to come from Arizona or Colombia. At present, in Taiwan (or even in Asia), only TULAB may be able to test these obsidians and confirm their origin.

Inclusions were confirmed by Micro-Raman. (GR7-Dual Laser)

Figure 1. Australasian tektites from Thailand and granular natural glass (obsidian) from Indonesia, Arizona, and Colombia.
Figure 2. Swirly structure in the tektite from Thailand and crystal inclusions in granular natural glass (obsidian) from three other origins, including cystallites, plagioclase, biotite, apatite, and zircon.

This inclusion was found in an unheated spinel, which was confirmed to be an octahedral magnesite crystal surrounded by a spherical zoning that appeared to consist of tiny exsolved particles. The inclusions were confirmed by Micro-Raman.

Zircon halos are a common inclusion in corundum, and are often found in many gemstones. This is a zircon crystal included in a faceted iolite with a rounded shape and surrounded halos consisting of small wings of fractures. Micrograph was taken with Gemscope GR7, and inclusions were confirmed with a Raman microscope.

A colorless Topaz of the customer was found to have some sub-metallic black to brownish red crystal inclusions, which were originally guessed to be rutile crystals, but were finally confirmed to be Tantalite ((Fe,Mn)Ta2O6) by micro-Raman. It is a common mineral in pegmatite, but a rare inclusion in gemstones.

This is an inclusion found in an aquamarine pear cabochon, with a flower-shaped pattern, which is actually a "hematite rose" observed in the direction of the basal plane. Such shapes or forms composed of regular and symmetrical pattern are usually called fractals geometrically. This photomicrograph was taken with Gemscope GR7 with 5MP electronic eyepiece at 100X magnification, and the inclusion was confirmed by micro-Raman(GR7).

Figure 1 is a bangle of black nephrite jade submitted to TULAB for identification sevice. The black color comes mainly from the large amount of graphite inclusions in nephrite. The Raman spectra of graphite usually show differences with the temperature of formation, therefore it is used as a "geothermometer" by geologists.
Typical Raman spectrum of graphite is shown in Figure 2. There are two Raman peaks, among which the G peak is related to the stretching vibration between carbon atoms in the molecular structure, and the D peak belongs to the vibration of the irregular hexagonal lattice structure of amorphous graphite. The Raman spectrum of this black nephrite jade bangle has actually revealed that the temperature is about 300°C, and many former researches on nephrite have also pointed out that the formation temperature of nephrite is generally 320∼420°C, and related study from China also pointed out that the homogeneous temperature of the liquid inclusions of the secondary black nephrite jade deposit at Xinjiang is between 200～400℃. In addition to admiring the "black as ink" that graphite brings to nephrite, the related research of Raman spectroscopy and gemology may further explore the formation or origin of the nephrite jade. However, in reality, this type of research cannot be used as evidence for nephrite origin directly. The origin determination of nephrite may also need other methods such as oxygen isotope, dating, and liquid inclusion.

The rounded crystal in the picture is a baddeleyite crystal in the spinel from Burma. Beddeleyite is a rare xenocrystal (ZrO2, monoclinic) and is usually produced in alkaline basalt or carbonate rock. The inclusion were confirmed by Micro-Raman (GR-7) and photographed with a 200X objective lens.

This was a white fibrous inclusion inside a peridot from Burma, and it looked similar to the horsetail inclusion in demantoid garnets. This inclusion was confirmed to be chrysotile by Micro-Raman. Chrysotile is one of the mineral members of the serpentine group, which is usually metamorphosed from olivine and related to ultramafic igneous rocks.

Hematite is one of the most common inclusion types in crystals and one of my favorites. No matter the commercial name given to them by the market is super7, strawberry quartz, auralite23 or hematoid quartz, there are usually various hematites with different morphological characteristics in these quartz.
Common hematite inclusion appearances include granular, hairline, Striped, flaky, dendritic, or radiated, all of which are popular with rock crystal collectors.
The photo contains four forms of hematite, all confirmed by Raman microspectroscopy.(Gemscope GR-7-Dual)

Photo by TULAB of Gem Research.

The inclusion is a heat-altered crystal close to the surface of a Be-diffused sapphire. After microscopic Raman analysis, it was found that the heat-altered crystal was not melted into glassy material but underwent a phase transformation to form hydroxylherderite instead.
This inclusion basically does not appear in natural corundum, and its composition is CaBe(PO4)(OH), which apparently resulted from the phase transformation of apatite xenocrystals [Ca5(PO4)3(F ,Cl,OH)] during the Be-diffusion process. Although Raman spectroscopy and inclusion can rarely be used as direct evidence for Be-diffusion treatment, this unique case provides another method for the detection of Be-diffused sapphires other than LA-ICP-MS or LIBS.
Inclusions confirmed by Micro-Raman (Gemscope Raman-GR7-Dual)
Photo by TULAB of Gem Research.
＃Bediffusion

Padparadscha sapphire is a very precious variety of corundum; it has a very unique color, a mixture of pink and orange. This color is quite rare in natural sapphires, but the jewelry industry has developed a beryllium diffusion process to produce this special color. Beryllium diffused sapphire is difficult to identify unless LA-ICP-MS or LIBS is used.
Empirically, some indicative inclusions in sapphire can assist in judging whether it has been beryllium diffused, such as the two blue dots in the photomicrograph. These blue dot inclusions are actually the rutile xenocrystals surrounded by a spherical blue color zoning which is a form of internal diffusion after beryllium diffusion treatment. These inclusions are rarely seen in the natural untreated padparadscha sapphire.
Photomicrograph taken with Gemscope 100X, expanded by depth of field. Photo by TULAB
＃bluedot

Dumortierite quartz usually refers to the rock crystal with the dumortierite needle inclusions and is mainly produced in Brazil. In most cases, dumortierite crystals are light blue in color, sometimes near colorless. In a few cases, some dumortierite crystals show beautiful medium to medium dark blue color. There are some extremely light-colored dumortierite quartz on the market, which is color-enhanced with blue dye to create the dark blue color; usually the dye would concentrate on the surface-reaching fissures.
The inclusions was confirmed by Micro-Raman (GR7-dual-laser Raman Microscope).

Various flaky inclusions are common in quartz, such as phlogopite, clinochlore, hematite, etc. The xenocrystal in the photo below is a muscovite crystal in a rock crystal, which has a pseudo-hexagonal crystal form. The viewing direction is exactly parallel to the basal direction of muscovite, therefore the crystal shows typical hexagonal appearance. The inclusion was confirmed by a Raman microscope (Gemscope GR-7), and the scale bar was 50 microns.

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這是一個包裹於緬甸橙紅色尖晶石中的白雲石內含物包裹體。因為具有八面體的外觀，如果只用顯微觀察視覺上鑑定，很可能被誤認為尖晶石含晶或負晶體。因此寶石學家若只透過顯微觀察判斷內含物種類時必須很謹慎。
事實上，如果這樣的內含物真的是尖晶石含晶，由於其折射率與主晶近乎相同，理論上應該幾乎看不到該含晶(折射率相近呈現低浮影)。
該內含物採顯微拉曼光譜儀鑑定確認，顯微照片放大倍率約為200X。
#尖晶石 #白雲石 #八面體 #緬甸 #拉曼光譜

This is a dolomite inclusion in an orange-red spinel from Burma. Since the appearance is like a regular octahedron, it may be mistaken for a spinel xenocryst or a negative crystal if visually judged. Therefore, gemologist should be very cautious to identify inclusions through microscopic observation alone.
In fact, if such an inclusion is really a spinel xenocryst, and its refractive index is almost the same as that of the host crystal, theoretically, it should be almost invisible (low relief).
This inclusion was confirmed by Raman microscope , and the magnification was about 200X.

This is a dolomite inclusion in an orange-red spinel from Burma. Since the appearance is like a regular octahedron, it may be mistaken for a spinel xenocryst or a negative crystal if visually judged. Therefore, gemologist should be very cautious to identify inclusions through microscopic observation alone.
In fact, if such an inclusion is really a spinel xenocryst, and its refractive index is almost the same as that of the host crystal, theoretically, it should be almost invisible (low relief).
This inclusion was confirmed by Raman microscope（Gemscope GR-7） , and the magnification was about 200X. Micrographs provided by TULAB of GEM RESEARCH, INC.

這是所長最喜歡的鈦晶之一，排列井然有序的金色針狀金紅石與黑色的赤鐵礦形成很強烈的對比。內含物以顯微拉曼光譜檢測確認，放大倍率約為100倍。
#金紅石 #赤鐵礦 #石英 #拉曼

This is my personal favorite rutilated quartz. The orderly arranged golden rutile needles and the black hematite form a strong contrast.
Inclusions were confirmed by a Raman microscope, and the magnification was 100X.

This is my personal favorite rutilated quartz. The orderly arranged golden rutile needles and the black hematite form a strong contrast.
Inclusions were confirmed by a Raman microscope (Gemscope GR7), and the magnification was 100X.
Photomicrograph provided by TULAB of GEM RESEARCH, INC.

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