• Economic and Environmental Geology
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• v.46 no.5
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• pp.375-390
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• 2013

The Kenticha rare-element (Ta-Li-Nb-Be) mineralized zone is located in ophiolitic fold and thrust complex of southern Ethiopia and was firstly discovered by joint exploration program of Ethiopia-Soviet in 1980s. It includes Dermidama, Kilkele, Shuni Hill, Kenticha, and Bupo pegmatites from south to north. The Kenticha pegmatite intruded parallel to NS-striking serpentinite and talc-chlorite schist, and is exposed approximately 2 km length and 400-700 m width. The Kenticha pegmatite is internally zoned and subdivided into lower quartz-muscovite-albite granite, intermediate muscovite-quartz-albite-microcline pegmatite, and upper spodumene-quartz-albite pegmatite, based on their mineral assemblage. The major, trace elements (e.g., Rb, Li, Nb, Ta, and Ga), and element ratios (e.g., K/Rb, Nb/Ta, Mg/Li, and Al/Ga) suggest that the fractionation and solidification of pegmatite have progressed from the lower towards upper pegmatite. In contrast, unlike general magmatic fractionation, Mg/Li ratios of the Kenticha pegmatite tend to be increased towards the upper pegmatite. It may result from post-magmatic hydrothermal alteration and/or interaction with upper ultramafic rock. Rare-element mineralization in Kenticha pegmatite concentrates on the upper pegmatite, which contains up to 3.0 wt % $Li_2O$, 3,780 ppm Rb, 111 ppm Cs, 1,320 ppm Ta, and 332 ppm Nb. Ore minerals in Kenticha pegmatite mostly include tantalite, spodumene, and lepidolite, and tantalite has an association with coarser quartz-spodumene and relatively fine sacchroidal albite. The tantalite is classified into Mn-tantalite as a function of $Mn^*[Mn/(Mn+Fe)]$ and $Ta^*[Ta/(Ta+Nb)]$ values. Its compositions ($Mn^*$, $Ta^*$, and Nb/Ta) between coarse and fine tantalites are different and the former is strongly enriched in Ta and depleted in Nb compared to latter one. In conclusion, rare-element mineralization in the Kenticha pegmatite may has occurred in the latest stage of magmatic fractionation.

• Economic and Environmental Geology
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• v.22 no.4
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• pp.327-339
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• 1989

Cassiterite, tantalite, columbite and tantalian rutile are found as accessory minerals in Soonkyoung tin-bearing pegmatites. These minerals occur as finely disseminated specks of up to micro-size in diameter and coarse grain size varying from 0.5-50mm in albite, muscovite and quartz assemblage. Cassiterite geneally shows a moderate to intense pleochroism, having a color brownish yellow to deep reddish brown. The substitution of $Ta^{+5}$, $Nb^{+5}$, $Ti^{+4}$ and Fe* for $Sn^{+4}$ in cassiterite ranges 0.01-0.10 mol%. The zoned cassiterite give a higher Ta/Nb ratios in margin than the ratios in core. This is due to the preferential $Ta^{+5}$ affinity to lower temperature during the crystallization of cassiterite. Tantalite-columbite and tantalian rutile occur in cassitertie with exsolution texture and/or infiltrate into the micro-fissures of cassiterite with micro quartz vein. The compositions of tantalite-columbite show the wide ranges of $Ta_2O_5$ : 14-46 wt.%, $Nb_2O_5$ : 60-28 wt. % and FeO*: 10.15 wt.%. The variation of chemical composition in tantalit-columbite exhibits the decreasing trends of $Mn^{+2}/M^{+2}+Fe^*$ with $Ta^{+5}/Ta^{+5}+Nb^{+5}$ increasing. These trends of vatiations indicate that the Ta/Nb fractionation are enhanced by higher Ta-complex activity in late stage of pegmatite consolidation and lower activity of F in agreements with the F-and Li-micas not to be developed in Soonkyoung tin-bearing pegmatite.

• Journal of the Mineralogical Society of Korea
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• v.28 no.1
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• pp.51-60
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• 2015

We applied gemological analytical approaches on Aquamarine from the Gilgit-Baltistan of Northern Areas, Pakistan. The standard gemological testing indicates that they are consistent with general characteristics of natural aquamarines. We have identified the inclusions of Tantalite-Mn by Raman analysis. It indicates that they occurs in association with the veins of Be-rich coarse pegmatite. And the results of chemical analyses, infrared absorption spectroscopy and Raman spectroscopy indicate that $H_2O$ molecules in channel mostly exist in Type-I and a little Type-II with low alkali ion. The comparison of relative peak intensity of FT-IR analysis can be used for prediction of $Na_2O$ content within not only emerald but also aquamarine.

• Economic and Environmental Geology
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• v.47 no.3
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• pp.255-263
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• 2014

Conflict minerals refer to minerals mined in conditions of armed conflict, especially as in the eastern provinces of the Democratic Republic of the Congo. The common conflict minerals are cassiterite, wolframite, coltan(columbite-tantalite ore), and gold, which are mined and extracted from the Eastern Congo. These minerals are essentially used in the manufacture of a variety of devices, including consumer electronics. To end the violent conflict in the Democratic Republic of the Congo (DRC) and in surrounding countries, it is necessary to block the supply route of conflict minerals which has been partially financed by the exploitation and trade of conflict minerals. The Dodd-Frank Wall Street Reform and Consumer Protection Act, passed into law in July 2010 and it contains requirements that U.S. companies report to the Securities and Exchange Commission(SEC) on the origin of conflict minerals and show due diligence of OECD. The goal of the act is to cut direct and indirect funding of armed groups engaged in conflict.