Photoluminescence Spectra of Emeralds from Colombia, Afghanistan, and Zambia

Thompson, D. Brian; Bayens, Christian J.; Morgan, Matthew B.; Myrick, Taylor J.; Sims, Nealey E.

doi:10.5741/gems.53.3.296

Cited by 1 publication

(1 citation statement)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Figure 13 exhibits the PL spectra of samples from Cunas, Chivor, Pakistan, and Zambia; and Figure 14 shows the Cr/Fe ratio versus R1 plot. Colombian emeralds range between 683.4 and 683.9 nm (Thompson et al, 2017;García-Toloza et al, 2019). In contrast, samples from Pakistan and Zambia range between 684.2 nm and 684.8 nm; Chivor emeralds range from 683.55 nm to 683.65 nm, and their average iron concentration is 800 ppm, which is notably lower than Cunas ~1039 ppm; the iron content of Zambian and Pakistan emeralds is higher than 14,000 ppm.…”

Section: Photoluminescencementioning

confidence: 99%

Mineralogy and Fluid Inclusions of the Cunas Emerald Mine, Maripí, Boyacá, Colombia

et al. 2021

View full text Add to dashboard Cite

The Cunas mine is currently one of the major producers of fine emeralds in Colombia; its emeralds typically display a magnificent green hue, which is highly appreciated in the world market. The mineralization is found in vanadium-rich black shales of the Muzo formation; emeralds occur in pockets within hydrothermal veins and breccias, consisting mostly of calcite, dolomite, albite, quartz, and minor pyrite, parisite-(Ce), and fluorite; hydrothermal alteration is pervasive and dominated by albitization and carbonatization. Emerald-hosted fluid inclusions are highly abundant and remarkably large and complex. Poly-phase inclusions are ubiquitous, occur both in emeralds and gangue minerals, and consist of two daughter crystals (typically halite and calcite or siderite; exceptionally parisite-(Ce)), a liquid brine, a CO2-N2-CH4-rich gas bubble, and occasionally minor liquid CO2. Vapor-rich inclusions were observed in quartz, and two-phase inclusions were identified in calcite and dolomite, thus suggesting a complex fluid evolution. Microthermometry analysis indicates the emerald-forming fluids were trapped at relatively low temperature ≈ 260-340°C and pressure ≈ 875-2400 kbar, with relatively high density —1.03 g/cm³—, and elevated salinity 39% NaCl eq. Wt.; other aqueous components detected include CaCl2, KCl, and FeCl2. Based on these data, we propose the emerald mineralization at the Cunas mine was originated by the mixing of two hydrothermal fluids of different sources; one fluid with high salinity derived from evaporite dissolution, responsible for the albitization of the host rocks; the second is a calcium-rich fluid evolved from connate waters, which was equilibrated by the interaction with calcareous and organic-rich wall rocks. As a result, emerald mineralization took place at structurally favorable sites where fluid mixing was promoted. The described geological and physicochemical features for the Cunas mine, are in agreement with an epigenetic sediment-hosted mineralization —Colombian-type— formed by the circulation and mixing of relatively low-temperature non-magmatic fluids.

show abstract

Section: Photoluminescencementioning

confidence: 99%