Li Guowu

Titanium, Ti, A New Mineral Species from Luobusha, Tibet, China

: We describe the new mineral species titanium, ideally Ti, found in the podiform chromitites of the Luobusha ophiolite in Tibet, Peoples Republic of China. The irregular crystals range from 0.1 to 0.6 mm in diameter and form an intergrowth with coesite and kyanite. Titanium is silver grey in colour, the luster is metallic, it is opaque, the streak is grayish black, and it is non-fluorescent. The mineral is malleable, has a rough to hackly fracture and has no apparent cleavage. The estimated Mohs hardness is 4, and the calculated density is 4.503 g/cm3. The composition is Ti 99.23–100.00 wt%. The mineral is hexagonal, space group P63/mmc. Unit-cell parameters are a 2.950 (2) A, c 4.686 (1) A, V 35.32 (5) A3, Z= 2. The five strongest powder diffraction lines [d in A (hkl) (I/I0)] are: 2.569 (010) (32), 2.254(011) (100), 1.730 (012) (16), 1.478 (110) (21), and 0.9464 (121) (8). The species and name were approved by the CNMNC (IMA 2010-044).

Tangdanite, a new mineral species from the Yunnan Province, China and the discreditation of ‘clinotyrolite’

Abstract Tangdanite, ideally Ca2Cu9(AsO4)4(SO4)0.5(OH)9·9H2O and monoclinic, is a new mineral species (IMA No. 2011-096) occurring in the Tangdan and Nanniping mines, southeast Dongchuan copper mining district, Dongchuan County, Kunming City Prefecture, Yunnan Province, P. R. China (26°11’N 103°51’E). The mineral is found in the oxidized zone (gossan) of an As-bearing Cu sulfide deposit and is clearly of supergene origin. Associated minerals are chalcopyrite, bornite, chalcocite, covellite, tennantite, enargite, cuprite, malachite, azurite, copper and brochantite. Crystals form radiating or foliated aggregates of flaky crystals up to 3 mm, flattened parallel to (100) and elongated along [001]. It is emerald green with a light green streak, translucent and has a pearly to silky lustre. It is sectile having perfect cleavage on {100} although neither parting nor fracture was observed. No fluorescence in long- or short-wave ultraviolet radiation was observed. The hardness is VHN50 42.0-43.6, mean 42.8 kg mm-2 (2-2 ½ on the Mohs scale). The density measured by pycnometry is 3.22 g cm-3 (Ma et al., 1980). The calculated density from the empirical chemical formula is 3.32 g cm-3. The compatability index gives 1 - (Kp/Kc) = -0.041 (good). The empirical formula (based on 36 O a.p.f.u) of tangdanite is Ca2.05Cu9.08(As1.03O4)4(S0.63O4)0.5(OH)9·9H2.04O. The simplified formula is Ca2Cu9(AsO4)4(SO4)0.5(OH)9·9H2O. The strongest five reflections in the X-ray powder-diffraction pattern [d in Å (I) (hkl)] are: 4.782(100) (3̄ 1 1), 4.333(71) (6 0 2), 5.263(54) (2̄ 0 2), 3.949(47) (8 0 2) and 2.976(46) (15̅ 1 1). The unit-cell parameters are a = 54.490(9), b = 5.5685(9), c = 10.4690(17) Å, b = 96.294(3)°, V = 3157.4(9) Å3, Z = 4. Its structure was solved and refined in space group C2/c, with R = 0.110.

Hydroxycalciopyrochlore, A New Mineral Species from Sichuan, China

Hydroxycalciopyrochlore, ideally (Ca,Na,U,□)2(Nb,Ti)2O6(OH), cubic, is a new mineral species (IMA2011–026) within the pyrochlore supergroup that was found occurring at the Maoniuping mine, Mianning County, Xichang prefecture, Sichuan Province, southwest China. The mineral is found in an alkali feldspar granite rare-earth ore deposit (26–27 Ma). Associated minerals include calcite, barite, celestine, albite, aegirine, aegirine-augite, fluorite, parasite-(Ce), thorite, thorianite, zircon, galena, sphalerite, magnetite, and pyrite. Crystals occur mostly as octahedra, and less often as dodecahedra and tetrahexahedra or combinations thereof. Some occur with an allotriomorphic habit with a thick triangular tabular form. Crystals generally range from 0.1 to 1 mm in size. The mineral is brownish-black, greenish-black and black on fresh sections with a brown streak. The crystal is translucent, and has a greasy lustre on fresh sections. It is metamict without any observed parting or cleavage and with a conchoidal fracture. The Vickers microhardness is 572 kg/mm2 (5–6 on the Mohs hardness scale). The density measured by hydrostatic weighing is 5.10(3) g/cm3. The strongest four reflections in the X-ray powder-diffraction pattern [d in A (I) hkl] are: 2.9657 (100) 2 2 2, 1.8142 (34) 0 4 4, 1.5463 (21) 2 2 6, 2.5688 (18) 0 0 4. The unit-cell parameters are a = 10.381(4) A, V = 1118.7(7) A3, Z = 8. The structure was solved and refined in the space group Fd3m with R = 0.09. The empirical formula is (Ca0.74Na0.58U0.40Ce0.05Fe0.02□0.21)2.00(Nb1.15Ti0.80Ta0.03Al0.01Mg0.01)2.00O6.02 [(OH)1.01F0.09]1.10, on the basis of 2 atoms of B pfu; the simplified formula is (Ca,Na,U,□)2(Nb,Ti)2O6(OH). Type material is deposited in the Geological Museum of China, Beijing, Peoples Republic of China, catalogue number M11800.

Oxynatromicrolite, (Na,Ca,U)2Ta2O6(O,F), a new member of the pyrochlore supergroup from Guanpo, Henan Province, China

Abstract A new mineral species of the pyrochlore supergroup, oxynatromicrolite (IMA2013-063), (Na,Ca, U)2Ta2O6O, was found in the No. 309 rare-metal granitic pegmatite vein, Guanpo, Lushi county, Henan Province, China, which is characterized by tantalum at the B site and oxygen at the Y site and is Na dominant at the A site. The mineral occurs as strongly metamict, and mostly euhedral octahedral crystals up to 0.05-0.20 mmacross. The measured density of an unheated sample is 6.580(4) g cm-3, and the calculated one is 6.506 g cm-3. Optically, the mineral is isotropic, with an index of refraction 1.999(5) and a reflectance of 11.88% (470 nm). When heated to 1000°C for 4 hours in N2, the mineral recrystallizes in the cubic system, with space group Fd3m and with unit-cell parameters similar those of other pyrochlore supergroup species: a = 10.420(6) Å, V = 1131.4(2) Å3. Electron microprobe analyses revealed the following composition of the mineral (in wt.%): Na2O 5.41, CaO 4.56, UO2 14.60, La2O3 0.16, Ce2O3 0.11, Nd2O3 0.13, PbO 0.62, Ta2O5 61.52, Nb2O5 8.21, Sb2O5 0.23, TiO2 0.05, SiO2 0.56, SnO2 0.29, F 1.04, H2O 1.50 (calculated to correspond to 0.47 H2O pfu), F≡O -0.44, sum = 98.53%, which corresponds to the empirical formula (Na0.99Ca0.46U0.31Pb0.02La0.01H2O0.21)Σ2.00 (Ta1.58Nb0.35Si0.05Sn0.01Sb0.01)Σ2.00O6 (O0.43F0.31H2O0.26)Σ1.00, represented by the simplified formula (Na,Ca,U)2(Ta,Nb)2O6(O,F). Oxynatromicrolite crystallized during the late-stage of formation for the No. 309 pegmatite dyke and is associated with quartz, albite, potassium feldspar, muscovite, kaolinite, tantalite-Mn, stibiotantalite, pollucite, spodumene, montebrasite, Hf-rich zircon, a red tourmaline, polylithionite, trilithionite, luanshiweiite-2M1 (IMA2011-102) and a hydrated derivative of oxynatromicrolite.