• journal_title：The Canadian Mineralogist
• Contributor：Igor V. Pekov ; Natalia V. Zubkova ; Nikita V. Chukanov ; Atali A. Agakhanov ; Dmitriy I. Belakovskiy ; László Horváth ; Yaroslav E. Filinchuk ; Elena R. Gobechiya ; Dmitry Yu. Pushcharovsky ; Murtazali Kh. Rabadanov
• Publisher：Mineralogical Association of Canada
• Date：2008-
• Format：text/html
• Language：en
• Identifier：10.3749/canmin.46.5.1343
• journal_abbrev：Can Mineral
• issn：0008-4476
• volume：46
• issue：5
• firstpage：1343
• section：Articles

A new mineral species, niveolanite, the first natural carbonate of beryllium, was found in the Poudrette pegmatite, Poudrette quarry, Mont Saint-Hilaire, Quebec, Canada. It is associated with albite, aegirine, natrolite, gonnardite, siderite, petersenite-(Ce), franconite, dawsonite, analcime, quartz, eudidymite, catapleiite, gaidonnayite, monazite-(Ce), calcite, adamsite-(Y), shomiokite- (Y), galena, sphalerite and rutile in cavities; earlier minerals are microcline, nepheline, annite, sodalite and zircon. Niveolanite occurs as soft fibrous (random, matted, radiating, subparallel, sheaf- or spray-like) aggregates up to 2 cm consisting of fibers up to 1.4 cm long and 0.01 mm thick. Rarely, aggregates of acicular crystals up to 1 cm long and 0.03 mm thick, elongate along [001], with a tetragonal or octagonal cross-section, and fibrous pseudomorphs after eudidymite are observed. Individual crystals of niveolanite are colorless and transparent. Aggregates are snow-white to pearl-white, with a silky luster. The density calculated for the empirical formula with 1.66 H₂O pfu is 2.06, whereas that for the less hydrous variety (1 H₂O pfu) is 1.82 g/cm³. Niveolanite is optically uniaxial positive, ω 1.469(1), ε 1.502(1). The IR spectrum is unique. The averaged chemical composition (Na, K and Ca were determined by electron microprobe, Be by ICP–OES, [CO₂ + H₂O] from loss on ignition, CO₂ by selective absorption) is: Na₂O 19.81, K₂O 0.07, CaO 3.88, BeO 16.65, CO₂ 29.81, H₂O 26.93, total 97.15 wt.%. The empirical formula calculated for 1 C apfu is: (Na_0.94Ca_0.10)_∑1.04Be_0.98(CO₃)_1.00(OH)_1.10·1.66H₂O. In moist air, niveolanite strongly absorbs molecular water; the process of its hydration–dehydration is easily reversible. Niveolanite is tetragonal, P4/mcc, a 13.1304(19), c 5.4189(11) Å, V 934.3(3) ų, Z = 8. The strongest ten lines of the X-ray powder diagram [d in Å (I)(hkl)] are: 13.01(100) (100), 9.20(62)(110), 4.343(27)(300), 3.611(34)(320), 3.269(22)(311), 3.256(95)(400), 2.693(44)(002), 2.605(37)(430,500), 2.489(60)(202), and 2.076(32)(620). The crystal structure was solved using a single crystal and synchrotron radiation, R = 0.0358. Niveolanite represents a new structure-type. Its structure includes isolated, infinite chains of BeO₂(OH)₂ tetrahedra linked via common OH groups; two other vertices of each Be tetrahedron are shared with (CO₃) groups, and Na cations occupy seven-fold polyhedra [NaO₆(H₂O)] forming columns. Chains of Be tetrahedra and columns of Na polyhedra are aligned along the c axis, just as broad channels in which H₂O molecules are located. The structural formula is: {(Na_0.9Ca_0.1)[(H₂O)_0.9(OH)_0.1]}{Be(OH)} (CO₃)·0–1H₂O. The idealized formula is: NaBe(CO₃)(OH)·1–2H₂O. The mineral was named from Latin niveus, snow-white, and lana, wool, alluding to the visual similarity of its aggregates to snow-white, fluffy flocks of wool. The cotype specimens are deposited in the Fersman Mineralogical Museum of Russian Academy of Sciences, Moscow, and the Canadian Museum of Nature, Ottawa.