Golden Sheen Sapphire
Gold Sheen Sapphire is a recognised variety of corundum displaying a phenomenal schiller and golden star asterism. The name Gold Sheen Sapphire and Golden Sheen Sapphire are interchangeable.
The term ‘gold sheen’ or ‘gold sheen effect’ was first described by the Emil Gem laboratory in Bangkok in 2014. Samples of the gemstone were tested to confirm they were true sapphire, with the description “The strong schiller phenomena is creating “GOLDEN SHEEN””[16].
Contents
1 Discovery and Source
2 Difference from other Varieties of Corundum
3 Optical effects
3.1 Color variations and Transparency
3.2 Color change
3.3 Asterism
4 Heating and treatment
5 Use in jewellery
5.1 Awards
6 References
1. Discovery and Source
The Journal of Gemmology reports the discovery was made in Eastern Kenya in 2009 and exported to Bangkok where its potential was realised by Bangkok gem dealer Tanzim Khan Malik[1].
2. Difference from other varieties of corundum
Gemologists T.M Bui et al compare Gold Sheen Sapphire with other known varieties of corundum. They note some similarity of chemical composition with Black Star Sapphire from Thailand, Australia and Laos[2] but conclude that “Despite the presence of similar heamatite-ilmenite inclusions in both types of sapphire, the large difference in appearances suggests the need for further investigations into their optical phenomena”[3].
An article published by the Gemological Institute of America’s Thailand Labrotatry in 2016 further updates the spectral characteristics of Gold Sheen Sapphire examining 14 stones describing them as The samples had yellow and green to blue bodycolor, were transparent to translucent” and “Their physical properties and inclusions were similar to those of gold sheen sapphires described in Bui et al. (2015)”[4]
Gemologists N. Narudeesombat et al, of The Gem and Jewelry Institute of Thailand also noted some “somewhat similar inclusions” between Golden Sheen and Non Sheen sapphires, but stated that “Comparatively, however, the golden sheen (set II) stones seemed to contain much higher amounts of platelets and needles intersecting in three crystallographic directions than those in the non-sheen (I) set. Thus, the combination of plentiful occurrence of exsolved reddish brown platelets plus short needles in three crystallographic directions in the basal pinacoid of sapphire is responsible for golden sheen star effects found in the set II samples.”[5]
Additional articles investigating these conclusions have further been published by GIA’s Tokyo Labotatry in 2018[6], Deutsche Gemmologische Gesellschaft eV (Germany) in 2018[7], Wooshin Gem Lab (Korea) in 2017[8], Polekiego Towarzystwa Gemmologigicznego (Poland) in 2018[9]
3. Optical effects
3.1 Color Variations and Transparency
Gold Sheen Sapphire displays a wide range of colors, often in the same gem, in addition to the prominent golden/bronze colour and sheen effect. It can range from opaque to transparent.
ICA GemlLab reported “blue, green and yellow”[17], Lotus gem laboratory reported “Transparent to opaque” and “Color (Daylight) Zoned bronze and blue”[18]. An AGL Laboratory report described a translucent gem that was “Bluish Orangish Brown”[19].
3.2 Color change
Golden Sheen Sapphire will exhibit mild to strong color change under warm, cool and direct sunlight.[citation needed]
Colour change characteristics have not yet been examined by any gemological laboratory.
3.3 Asterism
It is believed all cabochon cut Golden Sheen Sapphire will exhibit some degree of asterism.
Asterism characteristics have not yet been examined by any gemological laboratory.
4. Heating and treatment
There are no known heating or treatment methods for golden sheen sapphire.[citation needed] Testing of heat treatment on sample batches has resulted in diminishment of the gold sheen effect, reducing the appeal of the gemstone.[citation needed]
5. Use in jewellery
Golden sheen sapphire has been used in jewelry production by companies including:
William Travis Jewelry[10]
TVSN Australia[11]
David Yurman[12]
Cartier[13]
John Hardy Jewelry[14]
5.1 Awards
In 2016 a gold sheen sapphire ring by William Travis Jewelry won the American Gem Trade Association Savor Silver Award, Men’s Wear.[15]
6. References
[1] Bui T.N., T.N.; Deliousi, K.; Malik T.K., T.K.; De Corte, K. (2015). “From exsolution to ‘gold sheen’: A new variety of corundum” (https://gem-a.com/education/resources/application-and-downloads/syllabus/3250- from-exsolution-to-gold-sheen-a-new-variety-of-corundum-journal-of-gemmology-34-8-678-691/). Journal of Gemmology. 34 (8): 678–691.
[2] Bui T.N., T.N.; Deliousi, K.; Malik T.K., T.K.; De Corte, K. (2015). “From exsolution to ‘gold sheen’: A new variety of corundum” (https://gem-a.com/education/resources/application-and-downloads/syllabus/3250- from-exsolution-to-gold-sheen-a-new-variety-of-corundum-journal-of-gemmology-34-8-678-691/). Journal of Gemmology. 34 (8): 689.
[3] Bui T.N., T.N.; Deliousi, K.; Malik T.K., T.K.; De Corte, K. (2015). “From exsolution to ‘gold sheen’: A new variety of corundum” (https://gem-a.com/education/resources/application-and-downloads/syllabus/3250- from-exsolution-to-gold-sheen-a-new-variety-of-corundum-journal-of-gemmology-34-8-678-691/). Journal of Gemmology. 34 (8): 690.
[4] Update on Spectroscopy of “Gold Sheen” Sapphires Wasura Soonthorntantikul, Ungkhana Atikarnsakul, and Vararut Weeramonkhonlert https://www.gia.edu/gems-gemology/winter-2016-labnotes-update-spectroscopy-gold-sheen-sapphires
[5] Nalin Narudeesombat, Saengthip Saengbuangamlam, Thanapong Lhuaamporn and Thanong Leelawatanasuk (2016). “Golden Sheen and Non-Sheen Sapphires from Kenya” (PDF). The Gem and Jewelry Institute of Thailand (Public Organization), Bangkok, 10500, Thailand. July–August 2016: 283–284
[6] Makoto Miura, Yuske Katsurada, Kazuko Saruwatari (2018). “Update on trace-element chemical characteristics of golden sheen sapphire” Gems & Gemology, Summer 2018, 54, 238-241
[7] H. A. Hanni, U Henn (2016). “Golden Sheen Sapphire – Saphie mit goldfabigem Schimmer aus Kenia, Golden Sheen Sapphire from Kenya” Gemmologie, 65, June 2016, 49-52
[8] Bui T.N., T.N.; Deliousi, K.; Malik T.K., T.K.; De Corte, K. (2017). “Gold Sheen Sapphire : Newly Discovered Corundun” Wooshin Gemological Institute of Korea. 4, 2017 2-5
[9] Makiszczak A.I.P, Khan T.M., Manorotkul W., Burkhardt A. (2018). “Gold Sheen Sapphire fenomen z Kenii” Gems & Jewelry Polekiego Towarzystwa Gemmologigicznego, 8, 2018 18-21
[10] “2016 AGTA Spectrum Awards Winners”. www.agta.org. Archived from the original on 2016-11-17. Retrieved 2016-12-06.
[11] https://www.itvsn.com.au/product/306345&rrec=true
[13] https://en.wikipedia.org/wiki/Cartier_(jeweler)
[14] https://en.wikipedia.org/wiki/John_Hardy_(jewelry)
[15] “2016 AGTA Spectrum Awards Winners”. www.agta.org. Archived from the original on 2016-11-17. Retrieved 2016-12-06.
[16] Emil Gem Laboratory (Japan) Report No. 67238-2, 8th April 2014
[17] International Colored Gemstone Association GemLab Origin Report No. 2003180127004
[18] Lotus GEMology Laboratory Report No. 4103-3872
[19] AGL Laboratory Report No. 0009471 Password 7171
Sidebars and Graphics
| Gold/Golden Sheen Sapphire | |
|---|---|
 |
|
| General | |
| Category | Oxide mineral |
| Formula (repeating unit) |
Aluminium oxide, Al2O3 |
| Crystal system | Trigonal |
| Crystal class | Hexagonal scalenohedral (3m) H-M symbol: (32/m) |
| Space group | R3c |
| Identification | |
| Color | Typically metallic gold, copper or bronze, but varies |
| Crystal habit | As crystals, massive and granular |
| Fracture | Conchoidal, splintery |
| Mohs scale hardness | 9.0 |
| Luster | Vitreous |
| Specific gravity | 3.95–4.03 |
| Optical properties | Abbe number 72.2 |
| Refractive index | nω=1.768–1.772 nε=1.760–1.763, Birefringence 0.008 |
| Pleochroism | Strong |
| Melting point | 2,030–2,050 °C |
| Fusibility | Infusible |
| Solubility | Insoluble |
| Other characteristics | Coefficient of thermal expansion (5.0–6.6)×10−6/K relative permittivity at 20 °C ε = 8.9–11.1 (anisotropic).[1] |
