We found a match
Your institution may have rights to this item. Sign in to continue.
- Title
Gemmological Characteristics and Origin of Brown Olivine from Southeast Vietnam.
- Authors
Le Ngoc Nang; Pham Minh Tien; Pham Minh; Ho Nguyen Tri Man; Pham Trung Hieu
- Abstract
Olivine from Southeast Vietnam is notable for its dark brown colour, rather than the yellowish green appearance exhibited by typical gem-quality peridot. Discovered in 2020, this material occurs as xenocrysts weathered from the Xuan Loc alkali basalt. It is transparent to opaque, with a vitreous lustre. It has relatively high RIs (nα = 1.680-1.685 and nγ = 1.702-1.715) and relatively low birefringence (0.022-0.035), as well as elevated SG values (3.39-3.55). Inclusions consist of distinctive curly fibres of serpentine, and a hazy appearance of some stones is caused by amphibole particles. Raman and FTIR spectroscopy show features characteristic of olivine, and both powder X-ray diffraction and EDXRF chemical analysis indicate the olivine is forsterite. Based on geothermometer calculations from trace-element contents, the olivine crystallised from garnet peridotite in the temperature range of approximately 1400-1460°C and a pressure of 50 kbar. Although this brown olivine has limited usefulness as a gem material, its unusual properties and inclusions may draw the attention of gem collectors.
- Subjects
X-ray powder diffraction; FOURIER transform infrared spectroscopy; OLIVINE; RAMAN spectroscopy; ANALYTICAL chemistry; GARNET
- Publication
Journal of Gemmology, 2024, Vol 39, Issue 3, p260
- ISSN
1355-4565
- Publication type
Article
- DOI
10.15506/JoG.2024.39.3.260