• journal_title：The Canadian Mineralogist
• Contributor：Joel D. Grice ; Ralph Rowe ; Glenn Poirier ; Allen Pratt ; James Francis
• Publisher：Mineralogical Association of Canada
• Date：2009-
• Format：text/html
• Language：en
• Identifier：10.3749/canmin.47.1.193
• journal_abbrev：Can Mineral
• issn：0008-4476
• volume：47
• issue：1
• firstpage：193
• section：Articles

Bussyite-(Ce), ideally (Ce,REE,Ca)₃(Na,H₂O)₆MnSi₉Be₅(O,OH)₃₀(F,OH)₄, a new mineral species, was found in the Mont Saint-Hilaire quarry, Quebec. The crystals are transparent to translucent, pale pinkish orange in color, with a white streak and vitreous luster. Bladed crystals are prismatic, having forms {111̅} and {101̅}; they are elongate on [101], up to 10 mm in length. Associated minerals include aegirine, albite, analcime, ancylite-(Ce), calcite, catapleiite, gonnardite, hydrotalcite, kupletskite, leucophanite, microcline, nenadkevichite, polylithionite, serandite and sphalerite. Bussyite-(Ce) is monoclinic, space group C2/c, with unit-cell parameters refined from powder-diffraction data: a 11.654(3), b 13.916(3), c 16.583(4) Å, β 95.86(2)°, V 2675.4(8) ų and Z = 4. Electron-microprobe and secondary-ion mass spectrometric analyses give the average and ranges: Na₂O 7.63 (9.40–6.62), K₂O 0.05 (0.13–0.0), BeO 8.33 (SIMS), CaO 5.35 (5.95–4.17), MgO 0.03 (0.11–0.00), MnO 2.49 (3.00–1.71), Al₂O₃ 0.82 (1.54–0.39), Y₂O₃ 1.97 (2.68–1.51), La₂O₃ 2.65 (3.11–2.16), Ce₂O₃ 9.77 (11.22–8.15), Pr₂O₃ 1.23 (1.49–0.74), Nd₂O₃ 4.54 (5.13–3.91), Sm₂O₃ 0.99 (1.25–0.68), Eu₂O₃ 0.010 (0.25–0.0), Gd₂O₃ 1.03 (1.23–0.81), SiO₂ 38.66 (39.94–37.66), ThO₂ 3.31 (4.59–2.12), F 3.67 (6.39–2.54), S 0.03 (0.08–0), H₂O 4.12 (determined from crystal-structure analysis), for a total of 95.21 wt.%. The empirical formula based on the crystal-structure analysis, ideally showing 34 anions, is: 4{(Ce_0.823Nd_0.373Y_0.242Th_0.173Pr_0.103Sm_0.079Gd_0.078Eu_0.008)_∑1.879(Ca_0.775La_0.225)_∑1[Na_3.000(H₂O)_∑2.500Ca_0.544K_0.015]_∑6.055(Mn_0.485Na_0.402 Mg_0.012)_∑0.899(Si_8.897Be_4.605Al_0.222)_∑13.724O₃₀[F_2.67(OH)_1.33] _∑4}. The structure has been refined to an R index of 4.0% for 1134 unique, observed reflections. The structure has two chemically distinct layers parallel to (101̅): (1) a layer of [(Si,Be)O₄] tetrahedra, and (2) a layer of Ce–, Ca–, Mn–, Na–(O,F) polyhedra. Layers are cross-linked through shared O and F atoms. Significant amounts of OH and H₂O are present, as indicated in the IR spectrum and crystal-structure analysis for the Na-poor hydrated phase. One instance of a rarer Na-rich phase is observed. Based on the electron-microprobe data, the formula for the rarer Na-rich anhydrous phase is 4{(Ce_1.047Nd_0.466La_0.323Y_0.306Pr_0.131Sm_0.102Gd_0.084Eu_0.009Th_0.042)_∑2.510(Na_6.645Ca_0.701)_∑7.346(Si_9.521 Be_4.772)_∑14.293O_29.251F_4.749}. Comparing the structure of bussyite-(Ce) to that of other beryllium silicates, the topology of the layer of tetrahedra most strongly resembles that of semenovite-(Ce) and the closely related mineral harstigite.