Abstract
Abstract. Wumuite, ideally KAl0.33W2.67O9, is a new mineral species found in the Neoproterozoic Sinian light-weathered biotite–quartz monzonite in the southern part of the Panzhihua–Xichang region (Nanyang village: 26∘46′8.21′′ N, 101∘27′13.86′′ E), China. It is associated with quartz, orthoclase, albite, biotite, hornblende, kaolinite, ilmenite, goethite, hematite, zircon, zoisite, tourmaline, monazite-(Ce), allanite-(Ce), scheelite, tellurite, tewite, and an unidentified, potentially new mineral corresponding to WO3. Wumuite occurs as light green hexagonal tabular crystals, is up to 0.3 mm in diameter, and has a vitreous to adamantine luster and a white streak; i.e., it is transparent. The mineral is brittle with good cleavage parallel to {101¯0} and {0001}. It has a Mohs hardness of about 5–6 and a calculated density of 6.52 g cm−3. Electron microprobe analyses yielded the following (in wt % – average of 10 spot analyses of one sample): K2O 5.55, WO3 91.16, TeO2 0.59, and Al2O3 2.52, with a total of 99.82. The empirical formula for wumuite calculated on the basis of Oapfu=9 is K0.80(W2.68Al0.34Te0.03)∑3.05O9, ideally K(W2.67Al0.33)∑3O9 or KAl0.33W2.67O9. The strongest four diffraction lines [d Å (I) (hkl)] are 6.261(36)(010), 3.727(30)(001), 3.161(100)(020), and 2.413(40)(021). Wumuite is hexagonal, in space group P6/mmm, with a=7.2952(5) Å, c=3.7711(3) Å, V=173.81(2) Å3, and Z=1. The crystal structure was solved and refined to a reliability factor of R1[F2>4σ(F2)]=0.025 (wR2=0.072) based on 164 unique reflections (777 measured reflections, R(int)=0.011). Wumuite has a hexagonal tungsten bronze (HTB)-type structure. The layers of corner-sharing [(W,Al)O]6 octahedra, with the layers oriented normal to the short (3.7713 Å) c repeat and along with the W–O–W links, connect to form a hexagonal ring channel (tunnel). K is distributed in the hexagonal channel. An associated new mineral, tewite, which was discovered in the same area, also has a new tungsten bronze (TB)-type-related structure and has a genetic connection with wumuite in both back-scattered electron (BSE) images and synthetic experiments. The formation of wumuite is likely related to the nearby quartz-vein-type Au mineralization. The mineral was formed by a metasomatic reaction between W-rich hydrothermal fluids and the potassium feldspar in the monzonite.
Highlights
In 2014, we reported a new K–Te–W oxide mineral species, tewite (Li et al, 2019), discovered in the Neoproterozoic Sinian lightly weathered biotite–quartz monzonite in the southern part of the Panzhihua–Xichang region, Nanyang village, on the boundary between Panzhihua city, Sichuan Province, and Huaping County, Yunnan Province, China
During the further study of samples from this area, a new K– W mineral species with a hexagonal tungsten bronze structure, i.e., wumuite, was found in the same sample. This new mineral was named after the Wumu River near the source area, and the mineral species and its name have been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA2017-067a)
Base on the above discussions, wumuite is the only natural potassium tungsten bronze mineral found in nature, from the perspective of synthetic materials, there will be a great deal of similar potential new minerals as a result of the variations in the chemical components and crystal structure
Summary
In 2014, we reported a new K–Te–W oxide mineral species, tewite (Li et al, 2019), discovered in the Neoproterozoic Sinian lightly weathered biotite–quartz monzonite in the southern part of the Panzhihua–Xichang region, Nanyang village, on the boundary between Panzhihua city, Sichuan Province, and Huaping County, Yunnan Province, China. During the further study of samples from this area, a new K– W mineral species with a hexagonal tungsten bronze structure, i.e., wumuite, was found in the same sample. This new mineral was named after the Wumu River near the source area, and the mineral species and its name have been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA2017-067a).
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