Fluoro-Potassichastingsite From the Greenwood Mine, Orange County, New York: A New End-Member Calcic Amphibole

Abstract

Fluoro-potassichastingsite, ideally KCa 2 (Fe 2+ 4 Fe 3+ )Si 6 Al 2 O 22 F 2 , is found in compact aggregates of crystals up to 1 cm size on the waste-rock dump at the Greenwood mine, in Harriman State Park, Tuxedo, Orange County, New York, USA. It is associated with magnetite, diopside, enstatite, pyrrhotite, chalcopyrite, pyrite and, rarely, phlogopite. Fluoro-potassichastingsite is transparent, black to greenish in very thin fragments, and non-fluorescent in ultraviolet light; it has a vitreous luster and a greenish gray streak. The Mohs hardness is 6, D meas is 3.289 g/cm 3 , and D calc is 3.37 g/cm 3 . The {110} cleavage is perfect, and the fracture is conchoidal. It is biaxial negative, with a 1.668(2), b 1.688(2), g 1.698(2), 2V meas 40-70°, 2V calc 70°, Y = b, Z  c = 23°, and r < v. The observed pleochroism is X bluish green, Y green to brownish green, Z blue to light blue. The Gladstone-Dale compatibility index is superior, with 1 -(K P /K C ) = 0.012 (based on empirical formula and calculated density). The mineral is monoclinic, space group C2/m, a 9.9480 (3), b 18.1777(6), c 5.3302(2) Å, b 105.140(1)°, V 930.41(8) Å 3 , and Z = 2. The strongest eight X-ray powder-diffraction lines [d in Å(I)(hkl)] are: 8.H 2 O 0.70, O = (F+Cl) -1.08, sum 99.86 wt.%, which corresponds to the following crystal-chemical formula based on 24 [O + (OH) + F + Cl]: A (K 0.59 Na 0.25 ) S0.84 B analyses on a crystal fragment different than the one analyzed for major elements yielded the following trace-element concentrations (ppm): Cu 278.9, Rb 162.5, Y 343.2, La 257, Ce 568, Nd 156. The new species and name have been approved by IMA-CNMMN (2005-006).

Potassic-Hastingsite from the Kedrovy District (East Siberia, Russia): Petrographic Description, Crystal Chemistry, Spectroscopy, and Thermal Behavior

“…The observed variations in the end-member formula recognized by the IMA for hastingsite are reported in Table 1. Detailed crystal-chemical properties of the minerals have been investigated, sometimes using a multi-technique approach consisting of electron probe microanalysis, Mössbauer spectroscopy, and single-crystal X-ray refinements [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. However, relatively few studies on their structural behavior under non-ambient conditions have been made [22,23].…”