Alflarsenite, a new beryllium-silicate zeolite from a syenitic pegmatite in the Larvik plutonic complex, Oslo Region, Norway

作者：Raade Gunnar^*; Grice Joel D; Cooper Mark A

来源：European Journal of Mineralogy, 2009, 21(4): 893-900.

DOI：10.1127/0935-1221/2009/0021-1946

• alflarsenite
• new mineral species
• zeolite
• beryllium silicate
• crystal structure
• syenitic pegmatite
• Oslo Region
• Norway

Alflarsenite is a new beryllium-silicate zeolite with chemical composition close to NaCa(2)Be(3)Si(4)O(13)(OH)center dot 2H(2)O. It is a late-stage hydrothermal mineral from a syenitic pegmatite in the Tuften larvikite quarry, Tvedalen, Larvik, Vestfold, south Norway. Closely associated minerals are calcite, analcime and K-feldspar. Alflarsenite is monoclinic, P2(1), with a = 7.1222(4), b = 19.8378(11), c = 9.8071(5) angstrom, beta = 111.287(1)degrees, V = 1291.1(2) angstrom(3), Z = 4. The crystal structure was refined from single-crystal X-ray data to R1 = 0.045 for 3283 observed reflections. The zeolite structure is novel, consisting of intersecting channels: 5- and 8-membered channel rings along [010] and 3-, 6- and 8-membered channel rings along [100]. The strongest eight reflections of the X-ray powder-diffraction pattern [d(obs.) in angstrom (I) (hkl)] are: 9.095 (100) (001), 6.279 (42) (-111, 110),4.189 (32) (-122, 121), 3.972 (76) (-141, 140), 3.205 (37) (-113, 112), 2.964 (70) (-232, 230), 2.915 (92) (-133, 132), 2.757 (33) (-242, 240). Alflarsenite crystals are colourless (in aggregates pale beige) and bladed; they are flattened on (010) and elongate on [100] Identified crystal forms are {010}, {0-10}, {001} and {20-1}. Cleavage was not observed. The mineral is biaxial ( ) with refractive indices alpha 1.578(1), beta 1.580(1), gamma 1.583(1), measured at 590 nm. 2V (meas.) = 82(5)degrees from extinction curves and = 76(5)degrees by the Kamb method; 2V (calc.) = 79 degrees. The optical orientation is Z = b, X (boolean AND) a = 45(2)degrees. The Mohs hardness is similar to 4; D (calc.) = 2.605 g/cm(3).

• 出版日期2009-8