Backscattered electron (BSE) images of wumuite and some associated minerals. The image is published in an article distributed under the Creative Commons Attribution 4.0 License-. — Photo: Yuan Xue, Guowu Li, and Yingmei Xie · CC BY 4.0
Tewite
Tewite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula (K₁.₅ ₀.₅)(Te₁.₂₅W₀.₂₅ ₀.₅)₂W₅O₁₉.
It crystallizes in the orthorhombic crystal system (space group Pban).
Key properties: Mohs hardness 3.5–4; specific gravity 6.903; Light yellow to white streak; Adamantine luster; optically biaxial.
IMA symbol Tw, IMA status: approved, named in 2014.
Found in a biotite-quartz monzonite pluton near the contact zone with gabbro and nearby quartz-vein-type Au mineralization. Formed by metasomatic reaction of high-temperature fluids rich in W and Te with potassium feldspar in the monzonite.
It is found associated with Wumuite, scheelite, alkali feldspar, biotite, clinoamphibole, ilmenite, zircon, zoisite, tourmaline, monazite-(Ce), allanite-(Ce), tellurite.
Combination of the chemical symbols for two of its essential components Te and W.