Update on Emeralds from the Sandawana Mines, Zimbabwe

Zwaan, J. C. Hanco; Kanis, Jan; Petsch, Eckehard J.

doi:10.5741/gems.33.2.80

Cited by 23 publications

(12 citation statements)

References 23 publications

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“…The plot of MgO vs. Na 2 O presents a positive correlation (Figure 1), with a Na 2 O/MgO ratio being below 1 for most of the studied samples; only the studied Russian samples presented a ratio >1, with a 1.33 median and a 1.34 average (see Table 3). Data of samples from Brazil, Russia, Zimbabwe, Zambia and Madagascar are similar to previously published data measured with a microprobe [52,[55][56][57]77]; some of the Russian emeralds were found to contain higher MgO with a Na 2 O/MgO ratio <1 [55]. Chemical elements responsible for the colour of emeralds, such as Cr, V and Fe, can be seen in various amounts (e.g., 56 Fe up to 11200 ppmw for a sample from Madagascar).…”

Section: La-icp-mssupporting

confidence: 86%

Emeralds from the Most Important Occurrences: Chemical and Spectroscopic Data

Karampelas¹,

Al-Shaybani²,

Mohamed³

et al. 2019

Minerals

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The present study applied LA–ICP-MS on gem-quality emeralds from the most important sources (Afghanistan, Brazil, Colombia, Ethiopia, Madagascar, Russia, Zambia and Zimbabwe). It revealed that emeralds from Afghanistan, Brazil, Colombia and Madagascar have a relatively lower lithium content (7Li < 200 ppmw) compared to emeralds from other places (7Li > 250 ppmw). Alkali element contents as well as scandium, manganese, cobalt, nickel, zinc and gallium can further help us in obtaining accurate origin information for these emeralds. UV-Vis spectroscopy can aid in the separation of emeralds from Colombia and Afghanistan from these obtained from the other sources as the latter present pronounced iron-related bands. Intense Type-II water vibrations are observed in the infrared spectra of emeralds from Madagascar, Zambia and Zimbabwe, as well as in some samples from Afghanistan and Ethiopia, which contain higher alkali contents. A band at 2818 cm−1, supposedly attributed to chlorine, was observed only in emeralds from Colombia and Afghanistan. Samples with medium to high alkalis from Ethiopia, Madagascar, Zambia and Zimbabwe can also be separated from the others by Raman spectroscopy based on the lower or equal relative intensity of the Type I water band at around 3608 cm−1 compared to the Type II water band at around 3598 cm−1 band (with some samples from Afghanistan, Brazil and Russia presenting equal relative intensities).

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Section: La-icp-mssupporting

confidence: 86%

Emeralds from the Most Important Occurrences: Chemical and Spectroscopic Data

Karampelas¹,

Al-Shaybani²,

Mohamed³

et al. 2019

Minerals

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“…For comparison with the Fazenda Bonfim emeralds, we also collected LA-ICP-MS data on emeralds from two additional pegmatite-related deposits: Kafubu, Zambia (21 samples) and Sandawana, Zimbabwe (16 samples). The data reduction process for these localities used average SiO 2 concentrations of 63.0 and 62.8 wt.%, respectively (based on published electron microprobe and PIXE data; e.g., Zwaan et al, 1997Zwaan et al, , 2005Calligaro et al, 2000). Detection limits were typically in the lower parts per billion range, and analytical uncertainties were generally between 5% and 15%, based on the external reproducibility of the reference materials (Jacob, 2006).…”

Section: Methodsmentioning

confidence: 99%

Emeralds From the Fazenda Bonfim Region, Rio Grande do Norte, Brazil

Zwaan¹,

Jacob²,

Häger³

et al. 2012

G&G

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In Rio Grande do Norte State, rare-element mineralized granitic pegmatites have been known since the pioneering work of Johnston (1945) and Rolff (1946) in the Borborema Pegmatitic Province. In 2006, a team led by one of the present authors discovered emeralds in the Fazenda Bonfim region (figure 1; Cavalcanti Neto and Barbosa, 2007). The team was hired by Emprogeo Ltd. (Natal, Brazil) to explore for chromium, nickel, and platinum mineralization associated with ultramafic rocks, which were known to be present but had never been properly mapped. Emeralds were found in an area where geologists had previously focused on gold and rare-element mineralization. Several mines in this region (near the municipality of Lajes) had produced beryl and/or columbite-tantalite from pegmatites, but without any attention to the potential of ores related to ultramafic rocks. After the discovery of emeralds in the Fazenda Bonfim region, Mineração Vale Verde Ltd. (registered in June 2006) acquired the mining rights from Emprogeo Ltd. Exploration of the area, which comprises nearly 656 hectares, started in August 2006. Mineração e Comércio Itaobi Ltda. also owns several licenses close to this area, and Mineração Santo Expedito Ltda. is the holder of a nearby gold, tungsten, and bismuth mining concession. All have invested heavily in mineral exploration (sampling, drilling, mapping, and geochemical surveys). Despite these efforts and promising early results, the emerald mine has not yet begun production.

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“…LA-ICP-MS analyses of 111 gem-quality emeralds from the eight localities are summarized in table 2. The minor elements Na, Mg, and Fe and the trace elements K, Ca, Sc, V, Cr, and Cs were converted to oxide weight percent values for comparison with data reported on emeralds from the literature: Kaduna (Lind et al, 1986;Schwarz, 1996), Kafubu (Milisenda et al, 1999;Zwaan et al, 2005), Sandawana (Zwaan et al, 1997), Itabira-Nova Era (Schrader, 1987;Schwarz, 1990b;Kanis, 2001;Zwaan, 2001), Santa Terezinha (Hänni and Kerez, 1983;Schwarz, 1990a;Moroz et al, 1998;Pulz et al, 1998), Swat (Henn, 1988;Hammarstrom, 1989), Panjshir (Hammarstrom, 1989;Moroz et al, 1998) and Cordillera Oriental (Moroz et al, 1998). In addition, the trace elements Li, Ti, Zn, Ga, and Rb were all present in detectable quantities.…”

Section: Geographic Origin Determination Of Emeraldmentioning

confidence: 99%

Applications of Laser Ablation—Inductively Coupled Plasma—Mass Spectrometry (LA-ICP-MS) to Gemology

Abduriyim¹,

Kitawaki²

2006

Gems & Gemology

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Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is an important technique for quantitative chemical analysis. The authors have applied this minimally destructive technique to gemology to take advantage of its high spatial resolution, rapid and direct analysis of gemstones (whether loose or mounted), and precise measurement of a wide range of elements-even in ultra-trace amounts. This article summarizes LA-ICP-MS principles and describes the successful application of this technique to detecting beryllium diffusion treatment in corundum and identifying the geographic origin of emeralds. LA-ICP-MS is significantly less expensive than SIMS and more sensitive than LIBS, which is the least costly of the three instruments.

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Update on Emeralds from the Sandawana Mines, Zimbabwe

Cited by 23 publications

References 23 publications

Emeralds from the Most Important Occurrences: Chemical and Spectroscopic Data

Emeralds from the Most Important Occurrences: Chemical and Spectroscopic Data

Emeralds From the Fazenda Bonfim Region, Rio Grande do Norte, Brazil

Applications of Laser Ablation—Inductively Coupled Plasma—Mass Spectrometry (LA-ICP-MS) to Gemology

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