Abstract
H2O molecules in emerald channels have been extensively discussed over the past half century. Recent studies paid attention to their classification and coordination, but have mostly focused on the type related to Na+. There are few works on the other types, and the related infrared (IR) absorption bands are rather controversial. This paper investigated natural emeralds from China and Colombia by means of micro-Fourier transform infrared (μ-FTIR) spectroscopy, micro-confocal Raman spectroscopy, and laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS). The results suggested that doubly (IId) and singly (IIs) coordinated H2O molecules were incorporated in natural emerald channels. Type IId H2O predominated in those emeralds with relatively low alkali content. As the alkali content increased, the proportion of type IIs H2O rose, stemming from the decrease of the H2OII/Na+ apfu ratio. Moreover, IR bands of H2O corresponding to Li+ and Cs+ were tentatively ascribed here. IR bands for D2O and HDO in Colombian sample were observed in the range of 2600–2850 cm−1 and preliminarily assigned, which might be a potential tool for emerald origin determination. Our work expanded the existing classification of water molecules in emerald channels and redefined the controversial IR absorption bands.
Highlights
The charming color is due to trace amounts of Cr and/or V in the crystal structure
This paper investigates the chemical composition and spectroscopy of natural emeralds from Dayakou (China), and explores the coordination of alkali ions with H2O in the channel
We investigate the spectroscopy of emerald from
Summary
An emerald is the green gem variety of the mineral beryl with a general formula of. Be3 Al2 Si6 O18. Al3+ at octahedral (O) site and Be2+ at tetrahedral (T2) site These six-membered rings stack along the c-axis, forming large channels that are not identical in diameter. There are two types of structural positions in the uneven channels: twelve-coordinated 2a position The discourse about the positions of these cations and molecules in channel has raged unabated for over half a century [1–3,5,10,15] Cl− and neutral molecules (H2O and CO2), as well as noble gases, such as argon, helium, xenon, and neon [1–14].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
