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Oregon sunstone is a unique feldspar gemstone that displays a wide range of colors and optical effects due to the presence of metallic copper inclusions of various sizes and shapes. Most striking are the distinct green and red colors caused by copper particles, sometimes with strong red to green pleochroism. Recent computation work suggests that copper particles can strongly absorb and/or scatter light depending on the relative orientations of the feldspar crystal, the copper particles, and the polarization of the incident light, resulting in dramatically different appearances of the same crystal when viewed (or cut) along different directions. Common optical properties of Oregon sunstone are described and explained in detail in this paper, based on the optical theories of metallic nanoparticles in anisotropic media. Notably, it was found that the red to green colors observed can only be explained by considering both selective absorption and scattering from copper particles. The absorption and extinction spectra of the copper inclusions in Oregon sunstone are measured for different crystal orientations and polarizations. The scattering effect of the copper particles is quantified by subtracting absorption from extinction, the result of which agrees closely with the computed optical properties of spheroidal copper nanoparticles. The orientation of the anisotropic copper particles relative to the optical indicatrix of the feldspar is described. The correlation between the copper concentration profile and the "watermelon" color zoning in some Oregon sunstones is examined and discussed, along with a comparison to the color zones in treated, copper-diffused feldspar. Further studies on the diffusion and dissolution mechanisms of copper in feldspar crystals are required to fully understand the geologic processes that create these special gemstones in nature, which may provide additional methods to differentiate between treated and untreated stones. [ABSTRACT FROM AUTHOR]

The article focuses on the second annual Turquoise United Conference 2023 held at the Albuquerque Convention Center, aiming to unite members of the turquoise industry for discussion and collaboration. Topics discussed include sessions on laws governing turquoise jewelry, the implementation of a turquoise grading system, and courses on turquoise basics and collecting, with highlights on a highest-grade turquoise stone contest and research presentation on the Mona Lisa mine.

The article offers information about gem inclusions as mineral crystals or cavities filled with fluid and/or gas that occur in a host gemstone. It mentions that inclusions are important for determining the natural, synthetic, or treated character of a gem, and for establishing the likely geographic origin of a valuable colored stone.

The article discusses the identification of an exceptionally rare titanoholtite, a dumortierite supergroup mineral, based on its distinct physical properties and chemistry, which deviate from typical dumortierite characteristics, challenging previous assumptions about its composition and rarity.

Color is the most important quality for colored stones, one that is widely discussed and studied by gemologists. Understanding the color characteristics of a gemstone can provide a scientific basis to guide its cutting. This study uses visible spectroscopy to determine the unpolarized spectra of a uniaxial material from the polarized spectra (o-ray and e-ray) in order to predict the color of a uniaxial gem material when viewed in any direction. A seemingly intuitive way of doing this, by adding weighted amounts of the o-ray and e-ray absorption spectra, does not actually work for estimating the unpolarized spectra. The mathematically and physically correct way to reconstruct these unpolarized spectra is to add weighted polarized transmittance spectra and then to convert back to absorption if desired. This method allows color to be accurately predicted for a material when viewed in any direction as long as the polarized spectra and the viewing angle relative to the c-axis are known. This method has been verified by comparison with a synthetic V-bearing sapphire and a synthetic Cr-bearing sapphire cut into wafers (not faceted gemstones) at various angles relative to the optic axis. [ABSTRACT FROM AUTHOR]

The gem and jewelry trade has come to place increasing importance on the geographic origin of alexandrite, as it can have a significant impact on value. Alexandrites from Russia and Brazil are usually more highly valued than those from other countries. In 2016, GIA began researching geographic origin of alexandrite with the intent of offering origin determination as a laboratory service. Unfortunately, collecting reliable samples with known provenance can be very difficult. Alexandrite is often recovered as a byproduct of mining for other gemstones (e.g., emerald and corundum), so it can be difficult to secure reliable parcels of samples because production is typically erratic and unpredictable. The reference materials studied here were examined thoroughly for their trace element chemistry profiles, characteristic color-change ranges under daylight-equivalent and incandescent illumination, and inclusion scenes. The data obtained so far allow us to accurately determine geographic origin for alexandrites from Russia, Brazil, Sri Lanka, Tanzania, and India. Future work may help to differentiate alexandrites from other localities. [ABSTRACT FROM AUTHOR]

The gem world is rich with species of tourmaline such as the vivid greens of dravite, uvite, chromium-dravite, and vanadium-dravite; the pinks of elbaite and rossmanite; and the multicolored fluor-liddicoatite. To date, simple gemological tests to separate these various species, and many others of the tourmaline group, are lacking. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis is becoming a prevalent method to measure chemical composition in gemstones because it provides inexpensive, clean, fast, and largely nondestructive analyses. With adequate standards and calibration, this technique can quantitatively measure six common major elements in tourmaline (Na, Ca, Mg, Fe, Al, and Si) as well as trace elements (Cr, V). These data provide the basis for a simplified classification of gem tourmalines. Analyses of 14 tourmalines by both electron probe microanalysis (EPMA) and LA-ICP-MS for major and minor elements demonstrates that an LA-ICP-MS system with proper calibration, standardization, and normalization is capable of accurate measurements of six major elements in tourmalines, generally within ±10% error. While some volatile elements such as H, Li, B, and F cannot be measured reliably by this technique, a data reduction scheme can be implemented to calculate those elements based on select assumptions of concentrations of other major elements. Thus, LA-ICP-MS analysis is ideal for some tourmaline species determination in a gemological laboratory setting. The ability to provide a simple tourmaline species classification will enhance GIA identification reports and provide additional tools for identification. [ABSTRACT FROM AUTHOR]

The article discusses a unique partially non-nacreous blister pearl obtained from Pinctada radiata in Bahrain, detailing its unusual characteristics and scientific examination. Topics include the pearl's physical attributes, structural features, and reactions under various tests, shedding light on its formation and significance in gemological research.

The article focuses on the identification and examination of exceptionally large synthetic rutile stones, including a 110.18 ct specimen, which is the largest encountered in the GIA laboratory, highlighting their unique facet pattern, precision cutting, and variations in color.

The article offers information on discovery of color-change chrome grossular garnets from Ethiopia. Topics discussed include information on the ultraviolet (UV)-Vis-near infra-red (NIR) spectra. It mentions information on Vanadium and chromium concentration of grossular garnets. It presents information on Maxixe-type beryl.

Yogo Gulch in central Montana is one of the most important gem deposits in the United States. Although very little material has been recovered there in recent years, it has produced several million carats of rough sapphire over the course of its history (Voynick, 2001). These stones, known for their vibrant untreated blue color and high clarity, have always commanded a price premium, especially in sizes larger than 0.75 ct. This paper offers a thorough gemological characterization of Yogo sapphire, which may be unfamiliar to many gemologists. Fortunately, Yogo sapphires are unique and experienced gemologists can easily separate them from gem corundum of different geographic origins throughout the world, making it possible to determine the provenance of important stones from this deposit. [ABSTRACT FROM AUTHOR]

The article discusses the formation of gemstones within sedimentary rocks, highlighting their significance in documenting major geologic events and hosting economic deposits. Topics include the processes of weathering, erosion, and lithification in sedimentary rock formation, as well as the classification of sedimentary rocks based on mineral composition and depositional environments.

The article offers information on project offered by the Tiffany & Co. Foundation to the University of Delaware (UD) to promote responsible practices in the colored gemstone supply chain. It mentions information on contribution of the American Gem Trade Association (AGTA) and Workplace Health Without Borders (WHWB). It states that characteristics of stones that are easily confused, such as topaz and quartz.

The article reports on routine investigation of a parcel of sapphires from Ohn Bin Yee Htwet near Mogok in Myanmar. Topics include unusual composite inclusions that were observed, finding on the rough and irregular part of the inclusion, and hypothesis about the formation of these composite inclusions.

A type of pink pyrope garnet containing vanadium and chromium, believed to have been mined in Tanzania, appeared at the 2015 Tucson shows. The material shows a noticeable color difference from purplish pink under incandescent light (A) to purple under daylight-equivalent light (D65). This study reports a quantitative analysis of the difference in color between the two lighting conditions, based on the use of high-quality visible absorption spectroscopy to calculate CIELAB 1976 colorimetric coordinates. L*, a*, and b* colorimetric parameters were calculated for a wide range of path lengths as extrapolated from visible absorption spectra of thinner samples. Using this method, the path length of light through the stone that produces the optimal color difference can be calculated. This path length can then be used to determine the optimal depth range to maximize color change for a round brilliant of a specific material. The pink pyrope studied here can be designated as "color-change" garnet according to certain classification schemes proposed by other researchers. In many of these schemes, however, the material fails to exceed the minimum requirements for quantitative color difference and hue angle difference to be described as "color-change." Nonetheless, there is no simple solution to the problem of applying color coordinates to classify color-change phenomena. Also presented is a method by which spectra can be corrected for reflection loss and accurately extrapolated to stones with various path lengths. [ABSTRACT FROM AUTHOR]

The article presents the discussion on the news on gems. Topics include Fourier-transform infrared (FTIR) spectroscopy being considered a useful tool in revealing heat treatment of corundum; heating being the most common treatment for improving the color and/or clarity of corundum; and another important and desirable variety being blue spinel especially with a vibrant cobalt blue color.

The article presents the discussion on cushion-cut zircon with truly unusual color behavior including weak yellow fluorescence in short-wave UV and no fluorescence in long-wave UV.

The article discusses several research on gemstones published in different issues of various journals. These include properties of Russian synthetic emerald by K. Schmetzer in a 1996 issue of "Gems and Gemology," research on oscillatory zoned chrome lawsonite in the Tavsanli Zone. Turkey by S.C. Sherlock and A.I. Okay in a 1999 issue of "Mineralogical Magazine" and properties of synthetic blue spinel by M. O' Donoghue in a 1997 issue of the journal "Synthetic, Imitation & Treated Gemstones."

Notably, decrepitation halos are not indicative of heat treatment for sapphires originating from magmatic environments, including Montana sapphires (Winter 2018 Lab Notes, pp. 434-435). This 7.07 ct CVD-grown diamond came to the Carlsbad laboratory undisclosed as CVD, but advanced testing correctly identified this diamond's origin. Recently the Carlsbad laboratory received an intensely saturated purplish pink faceted sapphire for identification and origin report (figure 17). [Extracted from the article]

The article discusses gem cutting experiences of Jeff Hapeman of Earth's Treasury and his dealings in Montana sapphires.

The article reflects on the science and art of recutting fine gemstones.

Gemstones traded in markets globally can have extremely high values due to their physical appearance and, in some cases, their scarcity. Gemological laboratories provide identification services to determine gemstone species, growth origin, provenance, and the history of color- or clarity-enhancing treatments, all characteristics that can significantly affect gemstone values. These determinations are primarily conducted through microscopic analysis of the gem material and by identifying characteristic features in spectroscopic data acquired using nondestructive techniques. In addition, mildly destructive methods such as laser ablation--inductively coupled plasma--mass spectrometry may be employed to determine the trace element composition of a gem material. Traditionally, the diagnostic criteria used to determine geographic provenance or color/clarity treatment history are selected by trained specialists based on careful evaluation of large research datasets. Identifying the specific features that are useful for classification purposes can be time-consuming, and subtle diagnostic features may be overlooked. Machine learning enables rapid exploration of large, complex datasets in new ways. Hence, the application of machine learning algorithms may complement existing microscopic, spectroscopic, and geochemical approaches. This study examines the application of several machine learning models to gemstone classification problems involving natural alexandrite, laboratory-grown diamonds, and natural saltwater pearls. Using machine learning in a number of test cases, the authors achieved classification error rates as low as 5% or less for determination of provenance and detection of color treatment and were able to reduce the number of samples classified as indeterminate using conventional techniques by more than 50%. [ABSTRACT FROM AUTHOR]

The article focuses on the chromophore behaviors, including the 880 nm absorption band, in an irradiated pink sapphire, exploring the effects of radiation treatment on the color and trace element chemistry of the gemstone.

The article looks at sapphire mining at Potentate's mine in Montana, discussing the mining activities, gold recovery and sapphires recovered from the mine.

The article looks at gray spinel showcase at the American Gem Trade Association (AGTA) exhibition in Tuscon, Arizona.

The article reports on the documentation and inclusion of a rare sphalerite in the Namibian demantoid crystal. It offers brief details of the characteristics and elements of the stone, leading to its inclusion as calcite. It also provides images of the stone which shows its oblique fiber-optic illumination.

The article discusses the use of ultraviolet visible spectrometry and laser ablation-inductively coupled plasma mass spectrometry in identifying the color space of blue spinel. Topics include the multiple absorption bands of cobalt responsible for the production of blue color in spinel, the crystal chemistry of spinel which might be related to iron and the combination of cobalt iron responsible for changing blue to violet.

The article offers news briefs in the gemstone industry as of September 2017. New Era Gems has introduced the blue-green pyrope-spessartine garnet with high vanadium from Tanzania and Kenya. Also cited are the Montana sapphires mined by Potentiate Mining, and the developments in ruby mining and trading in Mozambique.

The article focuses on a synthetic color-change wakefieldite gemstone that exhibits a striking color change from pink or purple to blue or green, and displays strong fire due to its high dispersion.

The article focuses on orthorhombic aluminum oxide hydroxide mineral with the formula AlO is a relative newcomer to the jewelry scene with some stones possessing a captivating ability to change color between pale green, yellow, pink, and purple when viewed in different sources of light. Topics include the document a new find of purplish pink gem diaspore reportedly from Nangarhar Province, Afghanistan, and the transparent crystals of diaspore in sizes suitable for jewelry purposes.