Saltwater Pearls from the Pre- to Early Columbian Era: A Gemological and Radiocarbon Dating Study

Abstract

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Chemical Characteristics of Freshwater and Saltwater Natural and Cultured Pearls from Different Bivalves

“…Figure 1 is a binary plot of manganese oxide (MnO) and strontium oxide (SrO). This plot is similar to those previously presented using EDXRF chemical analysis [7][8][9], taking into account that the limit of detection for MnO is higher for EDXRF than for LA-ICP-MS. It was formerly published that the SrO/MnO ratio, measured with EDXRF, is separating freshwater (here presented as filled squares in the figure) from saltwater pearls, as it is >12 for saltwater pearls and <12 for freshwater pearls [8].…”

“…The rest of the studied natural saltwater pearls were six hundred seventy-one samples from Venezuela, part of a private collection. These samples were reportedly collected in the Pre to Early-Colombian Era from P. imbricata and kept in a jar for several years [9]. The pearls also have various shapes, sized from 2.9 to 19.5 mm, weigh from 0.2 to 47.5 carats and their colours vary from white to cream and sometimes light grey and light yellow.…”

“…However, for the freshwater samples, most present lower strontium and higher manganese samples with a ratio of <1. Chemical analysis of some freshwater samples might lead to wrong conclusions if the previously published plots and ratio are used [8,9], these are the freshwater (natural and cultured) pearls with 55 Mn <150 ppmw (i.e., MnO <ca. 194 ppmw) or 88 Sr >950ppmw (i.e., SrO >ca.…”

“…Energy dispersive X-ray fluorescence (EDXRF), a non-destructive method commonly used on gems, is applied to separate freshwater from saltwater samples [7][8][9]. Saltwater samples contain more Sr and less Mn than freshwater samples.…”

Detection of Color Treatment and Optical Brightening in Chinese Freshwater "Edison" Pearls

“…Trace element analyses were conducted using a Thermo Scientific ARL Quant'x energy-dispersive X-ray fluorescence (EDXRF) spectrometer (cal-ibrated with MACS-1 and MACS-3 carbonate standards) and a Thermo Fisher Scientific iCAP Qc inductively coupled plasma-mass spectrometry, coupled with an Elemental Scientific NWR213 laser ablation system (LA-ICP-MS) (three spots on each sample's surface, 55 μm spot size). More details on these gemological and instrumental methods for the application of pearl identification can be found in previously published papers (Zhou et al, 2017(Zhou et al, , 2019Nilpetploy et al, 2018;Homkrajae et al, 2019;Sturman et al, 2019;Tsai and Zhou, 2020).…”