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- Title
Agardite-(Nd) <sub>f</sub> NdCu<sub>6</sub> (AsO<sub>4</sub>)<sub>3</sub> (OH) <sub>6</sub>⋅3H<sub>2</sub>O, from the Hilarion Mine, Lavrion, Greece: mineral description and chemical relations with other members of the agardite-zálesíite solid-solution system.
- Authors
PEKOV, Igor V.; CHUKANOV, Nikita V.; ZADOV, Aleksandr E.; VOUDOURIS, Panagiotis; MAGGANAS, Andreas; KATERINOPOULOS, Athanassios
- Abstract
Agardite-(Nd), ideally NdCu6 (AsO4)3 (OH) 6⋅3H2O, has been approved by the IMA Commission on New Minerals, Nomenclature and Classification as a new mineral species, a Nd-dominant analogue of agardite-(Y), -(La) and -(Ce), a member of the mixite group. The material considered as the holotype was found in the Hilarion Mine, Agios Kon-stantinos (Kamariza), Lavrion District, Attiki Prefecture, Greece. Agardite-(Nd) occurs as thin, acicular to hair-like crystals up to 0.5 mm long and up to 5 um thick, elongate along [001], with hexagonal cross section. More commonly, agardite-(Nd), agardite-(Y) and/or agardite-(La) form rims (up to 3 urn thick) of zoned acicular crystals (up to 0.015 x 1.2 mm) with a core consisting of zalesiite. They are usually combined in sprays or radiating clusters up to 2 mm. Gradual compositional transitions among zalesiite, agardite-(Nd), agardite-(Y) and agardite-(La) are typical. The minerals of the agardite-zalesiite solid-solution system are associated here with zincolivenite, azurite, malachite and calcite in cavities of an oxidized ore mainly consisting of goethite and in cracks of supergene altered mica schist. Agardite-(Nd) is transparent, light bluish green, with white streak, and lustre vitreous in crystals and silky in aggregates. Crystals are brittle, cleavage is none observed, and fracture is uneven. Calculated density is 3.81 g/cm⊃3. Optically, agardite-(Nd) is uniaxial positive, co = 1.709-1.712, e = 1.775-1.780. Pleochroism is strong: O = pale turquoise-coloured, E = bright green-blue. Chemical composition of agardite-(Nd) (averaged of 6 electron microprobe analyses, H2O by difference) is: CuO 42.63, ZnO 3.52, CaO 2.15, Y2O3 1.27, La2O3 2.16, Ce2O3 0.38, Pr2O3 0.79, Nd2O3 3.05, Sm2O3 0.32, Gd2O3 0.40, Dy2O3 0.31, As2O5 33.65, H2Ocalc 9.37, total 100.00 wt. %. The empirical formula based on 3 As atoms is: Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. on other minerals of the agardite-zalesiite system from the Hilarion Mine are also given and discussed. Agardite-(Nd) is hexagonal, space group P63/m; unit cell parameters are: a = 13.548(8), c = 5.894(6) Å,V= 937(2) Å⊃3, Z = 2. The strongest reflections of the X-ray powder diagram (d, Å-Ihkl]) are: 11.70-100[100]; 4.443-22[111,120]; 3.545-18[211, 121]; 2.935-18[221, 400]; 2.695-13[112, 320, 230], 2.559-10[410], 2.453-30[212, 122, 231]. The type specimen is deposited in the Fersman Mineralogical Museum of Russian Academy of Sciences, Moscow.
- Subjects
LAVRION (Greece); GREECE; COPPER compounds; NEODYMIUM; MINES &; mineral resources; CLASSIFICATION; FUNCTIONAL groups; SOLID solutions; CLUSTERING of particles
- Publication
Journal of Geosciences, 2011, Vol 56, Issue 3, p249
- ISSN
1802-6222
- Publication type
Article
- DOI
10/3190/jgeosci.099