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Abstract:

Martinite, ideally (Na,Oe,Ca) (sub 12) Ca (sub 4) (Si,S,B) (sub 14) B (sub 2) O (sub 38) (OH,Cl) (sub 2) F (sub 2) .4H (sub 2) O, is a new mineral species from the Poudrette quarry, Mont Saint-Hilaire, Quebec. The mineral arose through the interaction of highly fractionated, hyperagpaitic fluids with sodalite syenite xenoliths. Martinite develops both as single crystals and as rosettes of triangular to roughly hexagonal plates varying from 50 mu m to a maximum of about 1 mm across. Individual crystals are typically <10 mu m in thickness and dominated by {001}, and colorless to mauve to purple in color. Associated minerals include aegirine, albite, erdite, eudialyte-group minerals, galena, langite, lueshite, lovozerite-group minerals, molybdenite, posnjakite, rasvumite, serandite, sazhinite-(Ce), sphalerite, terskite, ussingite, villiaumite, wurtzite and a number of unknown minerals, including several Cu (sub 2-x) S minerals (UK55 group), UK53a, UK73, UK82, UK91 and a lollingite-like mineral. The mineral has a vitreous luster, is transparent, has a white streak and shows no fluorescence in either short- or long-wave ultraviolet radiation. It has a Mohs hardness of 4; the crystals are inelastic, and have a perfect cleavage on {001}. It is brittle with an uneven fracture. The calculated density is 2.51 g/cm (super 3) . Martinite is non-pleochroic, optically biaxial (-), with alpha 1.529(1), beta 1.549(1), gamma 1.551(1) (for lambda = 590 nm), 2V (sub meas) = 38(1) degrees , 2V (sub calc) = 35(1) degrees ; no dispersion was noted. The optical orientation is X nearly equal c. On average, 19 electron-microprobe analyses gave: Na (sub 2) O 17.70, MgO 0.03, CaO 16.71, MnO 0.07, B (sub 2) O (sub 3) (calc.) 5.02, SiO (sub 2) 48.85, TiO (sub 2) 0.06, SO (sub 3) 2.30, F 2.18, Cl 1.09 and H (sub 2) O (calc.) 4.44, O = F+Cl -1.17, total 97.28 wt.%. The empirical formula (based on 46 anions) is: (Na (sub 9.19) Oe (sub 1.99) Ca (sub 0.82) ) (sub Sigma 12) (Ca (sub 3.97) Mn (sub 0.02) Mg (sub 0.01) ) (sub Sigma 4) (Si (sub 13.08) S (sub 0.46) B (sub 0.45) Ti (sub 0.01) ) (sub Sigma 14.00) B (sub 2) O (sub 38) (OH (sub 1.50) Cl (sub 0.50) ) (sub Sigma 2.00) (F (sub 1.84) OH (sub 0.16) ) (sub Sigma 2) .4H (sub 2) O. The principal absorption bands in the infrared spectrum include 3437, 1634 and 1011 cm (super -1) (shoulders at 1137, 1081, 898 and 862 cm (super -1) ) and five bands in the region 786-498 cm (super -1) . The mineral is triclinic, space group P[Formula: see text], a 9.5437(7), b 9.5349(6), c 14.0268(10) Aa, alpha 108.943(1), beta 74.154(1), gamma 119.780(1) degrees , V 1038.1(1) Aa (super 3) , Z = 2. The strongest seven lines in the X-ray powder-diffraction pattern [d in Aa(I)(hkl)] are: 13.18(100)(001), 6.58(43)(002), 2.968(37)(130), 3.29(34)(004,220), 2.908(27)(323), 3.02(17)(211), 2.800(17)(212). The structure of martinite has been refined to R = 6.30, wR (super 2) = 13.82%. The mineral is strongly layered, with sheets of tetrahedra (T), octahedra (O) and interlayer cations (X). The T layers are composed of six-membered rings of SiO (sub 4) tetrahedra linked by [(Si,B)]O (sub 4) and (BO (sub 4) ) tetrahedra. The sheets of octahedra are composed of edge-sharing Mphi (sub 6) octahedra (M: Na,Ca; phi : unspecified ligand) arranged in a closest-packed arrangement. The O sheets are effectively sandwiched between two symmetrically equivalent T layers (T (sub 2) , T (sub 2) ), producing a strongly bonded T-O-T unit. The interlayer component (X) houses poorly ordered Na polyhedra and H (sub 2) O molecules. Stacking of these principal components perpendicular to [001] results in a OT (sub 2) XT (sub 2) O module. Martinite is a member of the reyerite-gyrolite group. It represents the first B-bearing mineral of the group and the first mineral known to possess the OT (sub 2) XT (sub 2) O module. The name honors Robert Francois Martin (b. 1941), Professor of Geology at McGill University and long-time editor of The Canadian Mineralogist.

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GeoRef, Copyright 2018, American Geological Institute.<br/>2008-063126<br/>martinite<br/>Poudrette Quarry<br/>reyerite