| 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, blue, green 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] |
Golden sheen sapphire, (or goldsheen sapphire) is a recently discovered variety of corundum.[2] Goldsheen sapphire has been tested and confirmed in lab reports as "natural sapphire" by GIA, GIT, GRS, AIGS, Tokio gem labs and Lotus.
Goldsheen sapphire has a golden shine, almost like gold. Translucent blue, green or yellow material is sometimes present together with the gold.[3][2] Particularly prominent is hematite which will often result in the formation of geometric hexagonal patterns within the gemstone crystal.[4]
- ^ 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.
- ^ a b 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".
- ^ Journal of Gemmology. volume 35 no.5 https://gem-a.com/component/k2/volume/volume-35-no-5-2017-2-2 Pages 430-435
- ^ 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.