Publication details
Hingganite-(Nd), Nd2 Be2Si2O8(OH)2, a new gadolinite-supergroup mineral from Zagi Mountain, Pakistan
| Authors | |
|---|---|
| Year of publication | 2020 |
| Type | Article in Periodical |
| Magazine / Source | The Canadian Mineralogist |
| MU Faculty or unit | |
| Citation | |
| Web | https://doi.org/10.3749/canmin.2000039 |
| Doi | http://dx.doi.org/10.3749/canmin.2000039 |
| Keywords | hingganite-(Nd); new mineral; gadolinite supergroup; crystal structure; Zagi Mountain; Pakistan |
| Description | Hingganite-(Nd), ideally Nd-2 square Be2Si2O8(OH)(2), is a new gadolinite group, gadolinite supergroup mineral discovered at Zagi Mountain. near Kafoor Dheri, about 4 km S of Warsak and 30 km NW of Peshawar, Khyber Pakhtunkhwa Province, Pakistan. The new mineral forms zones measuring up to 1 x 1 mm(2) in loose prismatic crystals up to 0.7 cm long. where it is intergrown with hingganite-(Y). Other associated minerals include aegirine, microcline, fergusonite-(Y), and zircon. Ilingganite-(Nd) is dark greenish-brown, transparent, has vitreous luster and a white streak. It is brittle and has a conchoidal fracture. No cleavage or parting are observed. Mohs hardness is 51/2 -6. D-calc =4.690 g/cm(3). Hingganite-(Nd) is non-pleochroic, optically biaxial (+), alpha = 1.746(5), beta=1.766(5), gamma =1.792(6) (589 nm). 2 V-meas = 80(7)degrees; 2 V-ca(lc) = 84 degrees. Dispersion of optical axes was not observed. The average chemical composition of hingganite-(Nd) is as follows (wt.%; electron microprobe, BeO, B2O3, and Lu2O3 content measured by LA-ICP-MS;H2O calculated by stoichiometry): BeO 9.64, CaO 0.45, MnO 0.10, FeO 3.03, B2O3 0.42, Y2O3 8.75, La2O3 1.63, Ce2O3 12.89, Pr2O3 3.09, Nd2O3 16.90, Sm2O3 5.97, Eu2O3 1.08, Gd2O3 5.15, Tb2O3 0.50, Dy2O3 2.50, Ho2O3 0.33, Er2O3 0.84, Tm2O3 0.10, Yb2O3 0.44, Lu2O3 0.04, ThO2 0.13, SiO2 23.55, H2O 2.72, total 100.25. The empirical formula calculated on the basis of 2 Si apfu is (Nd0.513Ce0.401Y0.395 SM0.175Gd0.145Pr0.096DY0.068La0.051Ca0.04IEU0.031Er0.022Tb0.014Yb0.011Ho0.009Tm0.003Th0.003Lu1 0.001)(Sigma 1.979)(square 0 0.778Fe0.2152+Mn0.007)(Sigma 1.000)(Be1.967B0.062)Sigma 2.029Si2O8.46(OH)(1.54). Hingganite-(Nd) is monoclinic, space group P2(1/c) with a = 4.77193(15), b = 7.6422(2), c = 9.9299(2) A, beta= 89.851(2)degrees, V= 362.123(14) angstrom(3), and Z=2. The strongest lines of the powder X-ray diffraction pattern [d, angstrom (I, %) (hid)] are: 6.105 (95) (011), 4.959 (56) (002), 4.773 (100) (100), 3.462 (58) (102), 3.122 (68) (11 (2) over bar), 3.028 (61) (013), 2.864 (87) (121), 2.573 (89) (113). The crystal structure of hingganite-(Nd) was refined from single-crystal X-ray diffraction data to R = 0.034 for 2007 unique reflections with / > 2 sigma(/). The new mineral is named as an analogue of hingganite-(Y), hingganite-(Yb), and hingganite-(Ce), but with Nd dominant among the rare earth elements. |