Editors Thomas M. Moses | Shane F. McClure

DIAMOND laboratory recently examined two type Artificially Irradiated Type IIb IIb green brilliants, a 5.84 ct pear shape and a 0.30 ct round, that were color Saturated blue color is rare in natural graded as Fancy Dark gray-yellowish diamond, and various treatment methods green and Fancy Light yellow-green, have been developed to introduce or respectively (figure 2). enhance this effect. The more common Both were very clean microscopically. techniques include the annealing of type In cross-polarized light, the pear showed IIb diamonds under high-pressure/high- the tatami strain typical of a natural temperature (HPHT) conditions and the diamond. The round brilliant did not high-energy beam irradiation of light- exhibit any strain, but did show subtle colored type Ia/IIa diamonds. In the New color zoning (figure 3). DiamondView York laboratory, we recently examined a imaging of the pear shape revealed blue very rare case of a type IIb diamond artifi - luminescence with dislocations (straight cially irradiated to enhance its blue color. lines), indicating a natural diamond, This modified step-cut shield (13.70 Figure 1. The Fancy Deep green-blue while the round brilliant displayed a 10.75 5.09 mm) weighed 4.13 ct and ¥ ¥ color of this 4.13 ct type IIb diamond typical HPHT-synthetic growth pattern was color graded Fancy Deep green-blue is due to artificial irradiation. (figure 4). Spectroscopic analysis con - (figure 1). It displayed a clear color firmed a natural color origin for the pear concentration in the culet, an important and an as-grown color for the round visual indication of artificial irradiation. transmission window in the green–light brilliant. Both were verified as type IIb by Infrared absorption spectroscopy re - blue region. From these observations, the boron bands in their mid-infrared vealed a typical spectrum for a type IIb we confirmed that this diamond had spectra at ~2927 and ~2801 cm -1. diamond, with an intense 2800 cm -1 been artificially irradiated to improve Dislocations in a natural diamond peak corresponding to an optically its color. Strong plastic deformation occur during plastic deformation, which active boron concentration of ~40 ppb. indicated by high strain suggested that usually creates a brown color. In type A type IIb diamond with this size and the diamond had a significant brown IIb diamonds, the same process adds a boron concentration usually has a clear component before the treatment. This gray component to the blue color. In blue color (with a grayish or brownish also explains the strong green coloration this pear-shaped stone, however, plastic component, depending on the intensity observed after irradiation. deformation also contributed a yellow of plastic deformation) but not enough Type IIb diamonds are rarely irradiated component. The resulting combination saturation for a Fancy Deep grade. The to improve their color. This unusual of yellow and blue produced the 5.84 ct absorption spectrum in the UV-Vis sample allowed us the opportunity to diamond’s yellowish green bodycolor. region at liquid-nitrogen temperature examine the interaction of a vacancy Interestingly, the light yellow-green showed strong GR1 absorption and a defect (GR1) with other defects in a type synthetic diamond had a different cause weak 666.7 nm peak, resulting in a IIb diamond. of color. In addition to boron bands, a Wuyi Wang and Paul Johnson small amount of single substitutional nitrogen was detected at 1344 cm -1 in Editors’ note: All items were written by staff Type IIb Green, the mid-infrared spectrum. An earlier members of GIA laboratories. Natural and Synthetic study reported mixed type IIb + Ib syn - GEMS & G EMOLOGY , Vol. 48, No. 1, pp. 47 –52, Type IIb diamonds are typically blue, thetic diamonds with blue and yellow http://dx.doi.org/10.5741/GEMS.48.1. 47 . resulting from boron defects, and it is growth sectors (J. E. Shigley et al., “Lab- © 2012 Gemological Institute of America very unusual to see a distinct green color grown colored diamonds from Chat - in such diamonds. The New York ham Created Gems,” Summer 2004

LAB NOTES GEMS & G EMOLOGY SPRING 2012 47 G&G , pp. 128–145). The article pro - posed that the combination of these growth sectors produced a green or grayish green color in faceted samples. In the 0.30 ct synthetic diamond re - ported here, the same coloring mecha - nism—the com bined effect of a boron-dominated sector and an iso - lated-nitrogen sector—caused the yel - low-green bodycolor. In both samples, the cutting orientation was critical to the proper mixing of the blue and yel - low components. Therefore, other nat - ural and synthetic diamonds con taining Figure 2. These type IIb samples consist of a Fancy Dark gray-yellowish blue and yellow color com ponents may green natural diamond (5.84 ct, left) and a Fancy Light yellow-green syn - not show a green bodycolor. thetic diamond (0.30 ct, right). These type IIb specimens demon - strate that plastic deformation or a combination of boron and nitrogen defects can result in unexpected green coloration at the hand of a skilled diamond cutter. Kyaw Soe Moe

With Unusual Color Zoning An optical center with a broad absorp - tion band at ~480 nm is occasionally observed in some natural yellow-orange diamonds, as well as in “chameleon” diamonds. Yet little is known about this feature’s atomic structure or its mecha - Figure 3. In cross-polarized light, the pear shape showed the tatami strain nism of formation in natural diamonds. found in natural diamond (left, magnified 30×), while the synthetic round In the New York laboratory, we recently brilliant did not feature any strain but did show subtle color zoning (right, encountered a particularly interesting magnified 55×). manifestation of this optical center. A 0.50 ct rectangular diamond (4.43 ¥4.29 ¥2.80 mm) was color graded Fancy Intense orange-yellow. Its absorption spectrum in the mid-infrared region showed moderate concentration of A- form nitrogen and some unassigned peaks. A strong absorption band at ~480 nm, detected in the UV-Vis spectrum at liquid-nitrogen temperature, appeared to be the cause of the intense orange- yellow color. An outstanding feature of this diamond, visible during microscopic examination, was its distinct color zoning. The orange-yellow color was concen - trated in parallel zones separated by near-colorless areas (figure 5). This banded color distribution was matched by the Figure 4. DiamondView imaging of the pear shape revealed blue lumines - diamond’s fluorescence reaction to cence and dislocations corresponding to a natural origin (left), while the long-wave UV radiation. The orange- round brilliant showed growth zoning indicative of an HPHT-grown syn - yellow color zones showed very strong thetic diamond (right). yellow -orange fluorescence, while the

48 LAB NOTES GEMS & G EMOLOGY SPRING 2012 Large EMERALD with Gota de Aceite Structure Gota de aceite (Spanish for “drop of oil”) is a transparent angular or hexag - onal growth structure rarely seen in emerald (R. Ringsrud, “Gota de aceite : Nomenclature for the finest Colom- bian emeralds,” Fall 2008 G&G , pp. 242–245). The New York laboratory had the opportunity to examine a 24.25 ct Figure 5. The orange-yellow color emerald showing this phenomenon in this 0.50 ct diamond is concen - (figure 7). trated in parallel zones separated Microscopic observation revealed by near-colorless bands. transparent growth structures with an oily appearance throughout the stone (figure 8, left). The effect could even be near-colorless zones displayed strong blue seen with the unaided eye. Some of the Figure 7. This 24.25 ct Colombian fluorescence (figure 6). Micro scopic obser - structures displayed six well-defined emerald showed the rare gota de vation with crossed polarizers showed arms intercalated with six growth aceite growth structure. little internal strain, and there was no sectors, forming a 12-sided outline observable strain variation between the (figure 8, right); others showed an different color zones. From these obser - angular outline without arms. These Colom bian emerald. Individual and vations and the well-known fact that the structures occurred as individuals or in compact groups of colorless, transpar - 480 nm center luminesces yellow-orange elongated groups. The c-axis of each ent prismatic inclusions were identi - to UV radiation, it became clear that the growth structure was parallel to the fied by Raman spectros copy as quartz 480 nm center was distributed with a optic axis of the host emerald. Such (see photo in the G&G Data Deposi - zoned structure. It was also obvious that columnar growth zoning may have been tory at gia.edu/gandg), a well-known this banded structure was not associated developed by the parallel growth of inclusion in Colom bian emerald but with plastic deformation, a very common numerous sub-crystals, which were not previously reported in gota de cause of color zoning in natural diamonds. overgrown by the host emerald (E. J. aceite specimens. The stone also con - While the origin of the unusual distri - Gübelin and J. I. Koivula, Photoatlas tained strong planar color zoning, as bution of the 480 nm center in this of Inclusions in Gemstones , Vol. 3, well as partially healed fissures and diamond is unknown, the skillful orien - Opinio Publishers, Basel, Switzerland, fractures that showed evidence of clar - tation of the color banding by the cutter 2008, pp. 43 3– 434). ity enhancement. produced a face-up appearance that The sample’s jagged two- and Viewed in diffused light, the emerald’s received a Fancy Intense color grade. three-phase inclusions and spectro - green color was clearly concentrated Marzena Nazz scopic features confirmed it was a within the growth structures described

Figure 6. When the diamond was Figure 8. Fiber-optic illumination of the emerald clearly shows growth struc - exposed to long-wave UV radia - tures formed individually or in groups (left, magnified 25×). Some of the tion, the orange-yellow color growth structures consist of six well-defined, intersecting arms intercalated zones fluoresced very strong yel - between six growth sectors, creating a 12-sided outline (right, magnified 55×). low-orange, while the near-color - less zones showed strong blue fluorescence.

LAB NOTES GEMS & G EMOLOGY SPRING 2012 49 Figure 9. In diffused light, the emerald’s green color was strongly concen - Figure 10. These 76.63 ct oval and trated in the growth structures (left, magnified 30×). The growth struc - 34.53 ct freeform cabochons proved tures also showed high-order interference color in cross-polarized light to be manufactured composites that (right, magnified 15×). contain artificial metallic veining.

above, which also showed high-order ages in the white fragments and foli- expensive ornamental gem material. interference colors when viewed down ated metal flakes suspended in color - The second sample was a 34.53 ct the optic axis in cross-polarized light less plastic (figure 11) that was easily green and blue freeform cabochon with (figure 9). A high-resolution UV-Vis-NIR indented by a needle and produced an copper-colored metallic veining. Mag- absorption spectrum (available in the acrid odor when tested with a thermal ni fication and Raman analysis revealed G&G Data Depository) showed broad probe. Gemo logical testing gave spot it was composed of sand-sized quartz bands at ~425 and ~613 nm, and a doublet RI readings up to 1.65 that showed a grains suspended in a matrix of at 680 and 683 nm; all these features are birefringence blink. The sample was malachite, azurite, metallic flakes, and due to C r3+ . Interestingly, we also detected inert to long- and short-wave UV radi - colorless plastic that also produced an a very weak broad band at ~830 nm, ation. Raman analysis identified the acrid odor when tested with a thermal caused by F e2+ . The presence of this band, white fragments as calcite, which is probe (figure 12). A spot RI of 1.54 was not previously reported in Colombian consistent with the observed gemolog - consistent with the high percentage of emeralds, may be due to the high resolu - ical properties. EDXRF spec tros copy quartz grains present in the piece. The tion of the spectrum. revealed Cu and Zn as the dominant sample was inert to long- and short- So far, the gota de aceite structure elements in the veins. This alloy pro - wave UV radiation. EDXRF analysis has only been reported in Colombian duced an effective “gold” imitation. It showed that the metallic flakes were emeralds, and thus it provides a useful is clear from the cabo chon’s appear - com posed primarily of Cu with a small tool to identify geographic origin, along ance that it is intended to imitate gold- amount of Zn. A copper-colored matrix with the multiphase inclusions and veined quartz, an attractive and rather was appropriate for this imitation, spectroscopic features shown by these considering that azurite and malachite emeralds. are both copper minerals. Kyaw Soe Moe and Wai L. Win Figure 11. The imitation gold-in- quartz cabochon was composed of calcite veined by colorless Figure 12. Magnification of the Update on Artificial Metallic plastic containing very fine other cabochon shows small Veining in MANUFACTURED metallic flakes consisting of cop - rounded grains of quartz sus - GEM MATERIALS per and zinc. The foliated texture pended in a colored matrix of A Winter 2010 Lab Note (pp. 30 3–304) is distinctive of manufactured malachite and azurite with on artificial metallic veining in origin. Magnified 30×. metallic veining. Magnified 15×. composite turquoise speculated that this type of veining could appear in other gem materials. Such was the case with an interesting pair of cabochons (figure 10) that were recently examined in the Carlsbad laboratory. The first cabochon was a 76.63 ct oval composed of white angular frag - ments suspended in a yellow metal lic matrix. Magni fication revealed cleav -

50 LAB NOTES GEMS & G EMOLOGY SPRING 2012 This is the first time we have seen symmetrical, or even remotely uniform. Lazurite Inclusions in RUBY this manufacturing technique applied to The shapes of the nuclei were clearly The Carlsbad laboratory recently these particular materials, and it is reason - not natural but could not be readily examined a large 5.09 ct unheated ruby able to assume that additional composites identified as beads, either, due to their with a noteworthy inclusion suite. Stan- with artificial metallic veining could irregular and varied morphology. dard gemological testing gave refractive appear in a wide variety of combinations. With the client’s permission we cut indices of 1.762–1.770 and a strong red Nevertheless, the foliated appearance of open the orange-pink pearl, as its X-ray reaction to long-wave UV radiation. the metallic veining is quite diagnostic images revealed the most pronounced Examination with a desk-model spectro - of manufactured origin, regardless of the atypical structure, featuring one very scope revealed fine lines at 460, 470, and component material. straight edge. We sliced down the center 694 nm, along with a broad absorption Nathan Renfro and Amy Cooper lengthwise and found what appeared to band centered at 560 nm, which be a roughly cut piece of shell, evidently confirmed the stone was a ruby. used as the nucleus (figure 13, right). Microscopic examination showed dense Shell-Nucleated Freshwater The shell nucleus had an irregular shape clouds of fine iridescent rutile, unaltered Cultured PEARLS with some visible lustrous nacreous protogenetic carbonates, polysynthetic In November 2011, the New York lab - areas. The cross-section of the cultured twinning, and several “fingerprints.” The oratory received three large flat pearl showed a nacre thickness ranging overall inclusion suite, combined with baroque pearls for identification: one from ~1 to 2 mm. EDXRF spectroscopy the strong fluorescence, suggested a low- white, one orange-pink (figure 13, left), of the shell nucleus and the surrounding iron, marble-hosted ruby, most likely of and one multicolored. They ranged nacre indicated that both were of fresh - Burmese origin. water origin, as did the strong from 25.57 ¥ 16.16 ¥ 8.04 mm to 19.54 One particularly unusual type of lumi nescent reactions when exposed ¥ 16.44 ¥ 6.34 mm. Their shapes were inclusion stood out, however. Numerous similar to ones we have seen in the to X-rays. crystallographically aligned negative past that were nucleated with coin- or While it has become more common crystals (see Fall 2009 Lab Notes, p. 212) lentil-shaped beads, first mentioned in to nucleate freshwater cultured pearls were in-filled with a vibrant blue mineral G&G nearly 30 years ago (Summer with beads, this typically involves using that was identified by Raman analysis 1984 Lab Notes, pp. 109–110). Both symmetrical pieces of shell, either as lazurite (figure 14). Lapis lazuli is types of beads are often used for nucle - round (such as those commonly used known to occur in Myanmar, and this ation in freshwater mollusks to pro - in saltwater cultured pearls) or “fancy”- geologic overlap could provide an expla - duce flattened cultured pearls in shaped (as found in “coin pearls”). This nation for lazurite inclusions in a various shapes. is the first time we have examined corundum host. Standard gemological testing freshwater cultured pearls nucleated One of these contributors (VP) saw showed that all three were freshwater with roughly cut shell. Using these similar blue inclusions in rubies he pearls, but X-ray images revealed an relatively large shell nuclei produces a collected from Namya (or Nanyaseik), unusual internal structure (e.g., figure bigger cultured pearl in a shorter time, Myanmar, in December 2002. Analysis 13, center). All three contained what and the irregular shape results in a more of a sample purchased during that trip appeared to be a solid “nucleus” with natural baroque appearance. confirmed that the inclusions (figure 15) distinct edges, but the outlines were not Akira Hyatt were lazurite.

Figure 13. The orange-pink baroque cultured pearl on the left (25.57 × 16.16 × 8.04 mm) showed an asymmetrical “nu cleus” in X-ray images taken from two different orientations (center; arrows show outline of nucleus). It was sliced down its center lengthwise to reveal a roughly cut piece of shell that was apparently used as the nucleus (right).

LAB NOTES GEMS & G EMOLOGY SPRING 2012 51 analysis did not reveal the characteristic aragonite peaks at 1085 and 705/701 cm -1 (doublet) that would be expected for most shells. EDXRF chemical analy - sis indicated minimal levels of calcium (the major component of any natural shell), and traces of strontium (also a common constituent of shells). Both el - ements should have been more promi - nent if the sample was a true shell. Figure 14. A 5.09 ct ruby was host Figure 15. These blue inclusions Natural coiled gastropod shells to numerous lazurite-filled nega - in a 1.40 ct ruby, collected a show characteristic spiral structures tive crystals. Magnified 25×. decade ago in Namya, Myanmar, when viewed in cross section or consist of lazurite-filled negative examined by microradiography. Our crystals similar to those in figure microradiographic exami nation of this Blue inclusions in ruby are ex - 14. Magnified 40×. object (figure 17) clearly showed the tremely rare, and the presence of lazu - presence of natural shell with another rite in the 5.09 ct sample strongly they are coveted by religious devotees component—most likely a filler supports a Burmese origin. This find - who consider them to be natural repre - material used to add heft. An artificial ing is reinforced by the other inclu - sentations of Hindu deities. layer of material was then used to coat sions present in the stone and a The object did appear to be a shell, the assemblage and give it a realistic low-iron composition consistent with though the surface texture felt rather appearance. Burmese rubies. To our knowledge, smooth and the piece seemed some - This coated shell assemblage shows this is the first documented occurrence what hefty for its size. Closer examina - that even these simple religious icons of inclusions of lazurite in ruby. tion with a loupe and a gemological may be manufactured with the intent Nathan Renfro and Vincent Pardieu microscope indicated that the surface to deceive an unsuspecting buyer. was not shell but a resinous-looking Nick Sturman and substance that contained small gas bub - Hpone-Phyo Kan-Nyunt A Coated SHELL Assemblage bles. Nor were there any obvious shell- Whole shells are rarely submitted to GIA related characteristics such as flame for identification, so the Bangkok labora - structure or evidence of parasite holes or tory was interested to see such a channels within the shell. When ex - PHOTO CREDITS specimen recently. The specimen (figure posed to long-wave UV radiation, the Jian Xin (Jae) Liao—1, 2 (left), 5, 6, 7, 16) weighed 240.5 g and measured 132 sample flu oresced a weak-to-moderate and 13; Sood Oil (Judy) Chia—2 (right); Kyaw Soe Mo e—3, 4, 8, and 9; Robison 69 56 mm. The client wanted a report chalky uneven yellow rather than the ¥ ¥ McMurtry—10; Nathan Renfr o—11, 12, identifying it as a natural seashell. Such more commonly encountered blue reac - and 14; Vincent Pardieu—15; Nuttapol right-handed conch shells are rare tion, further adding to our doubts about Kitdee—16; Artitaya Homkraja e—17. compared to left-handed varieties, and the nature of the specimen. Raman

Figure 16. This specimen (13.2 cm Figure 17. A microradiograph of the thicker end of the specimen (left long) proved to consist of a natu - image) shows the spiral shell structure and some of the filler material ral shell that contained a filler (whiter area on far right side). The microradiograph on the right shows material and was covered by an part of the chamber area of the shell (A) and some of the filler used within unidentified artificial coating. the item (B).

52 LAB NOTES GEMS & G EMOLOGY SPRING 2012