ALFREDSTELZNERITE: A NEW SPECIES OF CALCIUM BORATE HYDRATE FROM THE SANTA ROSA MINE, SALTA, NORTHWESTERN ARGENTINA

作者：Angel Galliski Miguel; Cooper Mark A; Florencia Marquez Zavalia Maria; Hawthorne Frank C

来源：The Canadian Mineralogist, 2010, 48(1): 123-128.

DOI：10.3749/canmin.48.1.123

• alfredstelznerite
• new mineral species
• borate
• Sijes
• Argentina

Alfredstelznerite is a new borate species of composition Ca(4)(H(2)O)(4)[B(4)O(4)(OH)(6)](4) (H(2)O)(15), discovered at the Santa Rosa mine, a Tertiary borate deposit in Sijes, Salta, northwestern Argentina. The mineral occurs as mm-sized white fibroradial aggregates consisting of fine acicular colorless crystals up to 30 mm wide and up to 5 mm long, associated with colemanite, hydroboracite, ulexite, inyoite, gypsum and anhydrite, with minor meyerhofferite, nobleite, gowerite, inderborite, inderite, orpiment and realgar. The crystals of alfredstelznerite are euhedral, elongate along [001], with {010}, {hk0}, {100}, {hkl} and {hkl} as common crystallographic forms. The cleavage is perfect parallel to {010}, the hardness is 2, the streak is white, the luster is vitreous to silky, the density in g/cm(3) is 1.77(1)(meas) and 1.775(calc). Alfredstelznerite is biaxial positive with alpha = 1.476(3), beta = 1.478(3), gamma = 1.494(3), 2V(calc) = 39 degrees (for lambda = 589 nm); it has neither pleochroism nor dispersion. The optical orientation is X = b, Y = c, Z = a; the compatibility index is 0.022. Alfredstelznerite is orthorhombic, space group Pca2(1), a 12.161(2), b 40.477(8), c 10.1843(17) angstrom, V 5013(3) angstrom(3), Z = 4. The strongest six X-ray powder-diffraction lines [d in angstrom(I)(hkl)] are: 10.501(10)(120), 5.226(7)(201), 3.837(7)(222), 3.118(7b)(322), 2.612(6)(402) and 2.538(6)(004). Electron-probe microanalysis, combined with thermogravimetric analysis and crystal-structure refinement, gives the following ideal composition (in wt.%): B(2)O(3) 41.57, CaO 16.74, H(2)O 41.69. The empirical formula, normalized on the basis of 59 anions = 16 O(2-) + 24 (OH)(-) + 19 H(2)O, gives Ca(4.07)(H(2)O)(4)[B(3.99)O(4)(OH)(6)](4) (H(2)O)(15) or, ideally, Ca(4)(H(2)O)(4)[B(4)O(4)(OH)(6)](4) (H(2)O)(15).

• 出版日期2010-2