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Golden sheen sapphire

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Gold/Golden Sheen Sapphire
General
CategoryOxide mineral
Formula
(repeating unit)		Aluminium oxide, Al2O3
Crystal systemTrigonal
Crystal classHexagonal scalenohedral (3m)
H-M symbol: (32/m)
Space groupR3c
Identification
ColorTypically metallic gold, copper or bronze, but varies
Crystal habitAs crystals, massive and granular
FractureConchoidal, splintery
Mohs scale hardness9.0
LusterVitreous
Specific gravity3.95–4.03
Optical propertiesAbbe number 72.2
Refractive indexnω=1.768–1.772
nε=1.760–1.763,
Birefringence 0.008
PleochroismStrong
Melting point2,030–2,050 °C
FusibilityInfusible
SolubilityInsoluble
Other characteristicsCoefficient of thermal expansion (5.0–6.6)×10−6/K
relative permittivity at 20 °C
ε = 8.9–11.1 (anisotropic).[1]

Golden Sheen Sapphire, (or gold sheen sapphire) is a variety of corundum. Gold sheen sapphire has been tested and confirmed in lab reports as 'natural star sapphire' by GIA, GIT, GRS, AIGS, Tokio gem labs and Lotus.

Gold sheen sapphire can have a stunning golden shine, almost like metal (see picture). However, there is also low quality material, which is less desirable. It has the same color, chemical properties[2][3] and features as black star sapphire, also known as natural star sapphire or golden sapphire. Translucent blue, green or yellow material is sometimes present together with the gold.

Particularly prominent is hematite which will often result in the formation of geometric hexagonal patterns within the gemstone crystal.[4]

Questions regarding evidence and claims

Two articles from the Journal of Gemmology state that both black star and gold sheen are high in iron and titanium oxide, which accounts for the brown/black color. They have inclusions of ilmenite, hematite (gold color) and magnetite (black). Both exhibit asterism and hexagonal growth, a lack of UV fluorescence, healed fractures and polysynthetic twinning (parallel lines). Although declared as a "new variety" in 2015,[5] there is no question that goldsheen is 'natural star sapphire' as confirmed by laboratory reports. Natural star sapphire is also known as black star sapphire, [6] [7] which comes from more than ten countries in the world. [8][9]

Source

GIA Tokyo [10] and Gems and Jewellery [11] admitted in 2018 that the location is not known. GIA [12] and JoG [13] mention that there is no evidence of gemstone deposits in the flat border region near Somalia.

Previously, it was claimed in the Journal of Gemmology (JoG),[14] that the source is a depleted mine in Kenya close to the border of Somalia. TJN Colors, GIT and In Color [15][16][17] also previously published that the origin was Kenya.

Optical effects

Gold Sheen Sapphire has a subtle effect of colour change. This means that the golden surface shines strongly when the light hits it directly. It will also reflect the colour of light being shined. What this means is that it will look different under cold white light as compared to more natural soft yellow light.

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]

Use in jewellery

Golden sheen sapphire has been used in jewelry production by companies including

Awards

In 2016 a gold sheen sapphire ring by William Travis Jewelry won the American Gem Trade Association Savor Silver Award, Men's Wear.[18]

References

  1. ^ Harman, Alang Kasim; Ninomiya, Susumu; Adachi, Sadao (1994). "Optical constants of sapphire (alpha-Al2O3) single crystals". Journal of Applied Physics. 76 (12): 8032–8036. Bibcode:1994JAP....76.8032H. doi:10.1063/1.357922.
  2. ^ Journal of Gemmology. volume 35 no.5 https://gem-a.com/component/k2/volume/volume-35-no-5-2017-2-2 Pages 430-435
  3. ^ Journal of Gemmology. volume 34 no.8: pages 678–691. 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".
  4. ^ 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: 282–288.
  5. ^ 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". Journal of Gemmology. 34 (8): 678–691.
  6. ^ Bui T.N.; Entremont, Pascal; Gauthier. Jean-Pierre; (2017) "Large 12-Rayed Black Star Sapphire from Sri Lanka with asterism caused by Ilmenite Inclusions" (https://gem-a.com/component/k2/volume/volume-35-no-5-2017-2-2). Journal of Gemmology. volume 35 no.5 Pages 430-435.
  7. ^ 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.
  8. ^ AJS Gems, "Black Star Sapphire Gemstone Information" (2019) (https://www.ajsgem.com/gemstone-information/black-star-sapphire-27.html)
  9. ^ Hughes, Richard, "Moontown: A history of Chanthaburi, Thailand and Pailin, Cambodia" (2011) (http://www.ruby-sapphire.com/chanthaburi-history-of-moontown.htm)
  10. ^ Katsurada, Y; Miura M.; Saruwatari, K. "Golden Sheen Sapphire and Syenite/Monzonite–Hosted Sapphire From Kenya" GIA Tokyo: Gems & Gemology, Fall 2018, Pages 322-323.
  11. ^ Bui T.N. "Shimmering Sapphires" (https://gem-a.com/news-publications/gems-jewellery) Gems and Jewellery: Winter 2018, P36-39.
  12. ^ Katsurada, Y; Miura M.; Saruwatari, K. "Update on trace-element chemical characteristics of golden sheen sapphire." (https://www.gia.edu/gems-gemology/summer-2018-gemnews-update-on-trace-element-chemical-characteristics-of-golden-sheen-sapphire) Spring 2018, Vol. 54, No. 2.
  13. ^ 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". Journal of Gemmology. 34 (8): 678–691.
  14. ^ 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". Journal of Gemmology. 34 (8): 678–691.
  15. ^ Wheat, Barbara; “Aesthetic to the core” (2016) (http://www.tnjcolors.com/Issues/V3_I2/V3_I2.html). TJN Colors volume 3, issue 2. Pages 60-61.
  16. ^ Unninayar, Cynthia; "Gold Sheen Sapphires – From Gold Mine to Market" (2018) (https://gemstone.org/incolor/38/92/). In Color: Summer 2018, Pages 92-95.
  17. ^ "Golden Sheen and Non-Sheen Sapphires from Kenya" (https://www.git.or.th/eng/testing_center_en /lab_notes_en/glab_en/2016/11/D5-A0210-1.pdf)(PDF). The Gem and Jewelry Institute of Thailand.
  18. ^ "2016 AGTA Spectrum Awards Winners". www.agta.org. Archived from the original on 2016-11-17. Retrieved 2016-12-06.
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