UNIDENTIFIED SOFT, FIBROUS, SILVER-GRAY MINERAL FROM THE QUARRY AT FOUNTAIN, EASTERN NORTH CAROLINA

This mineral occurs as interior coatings on seams filled with quartz and blue NaFe amphibole. The host rock is a metamorphosed, early Paleozoic peralkaline granite. The mineral fibers are length slow and show parallel extinction and slight pleochroism (slower ray shows more absorption). The refractive indices are slightly greater than 1.700 and the birefringence is low 1^st order. Light absorption is very strong; the light brownish color is only visible in grains thinner than 0.03 mm. XRD powder runs and patterns from fiber clusters in different orientations, some spinning, some not, gave the following d-spacings: *17.46 (*high peak); *11,42 (max peak height); ^9.845 (^ intermediate peak); ‘8.183 (‘ low peak); ‘7.397; ‘6.792; ^5.997; ^5.782; ‘5.392; ‘5.244; ‘4.939; ^4.477; ‘3.987; ‘3.659; *3.285; ^3.255; ‘3.231; ‘3.093; ^2.935; ^2.888; ^2.580; and ‘2.529. Possible overlaps with peaks from quartz, NaFe amphibole, albite, and barite, known contaminants in the samples, compromise most peaks with 2-theta > 35º. An attempt to obtain XRD data from a single, very thin fiber failed. The chemical composition via microprobe is SiO2 (35.07), TiO2 (9.31), Al2O3 (1.64), Fe2O3 (18,72), MgO (0.49), CaO (2.74), MnO (6.77), FeO (12.20), K2O (0.77), Na2O (0.73), F (0.74), Cl (0.02), and Sum (89.20) corrected for O = F and O = Cl. Total Fe as FeO, was partitioned based on an Fe3+/FeT of 0.62 determined by Mossbauer spectrometry. The XANES absorption spectrum for Mn fairly closely matches that of Mn in MnO, indicating that the Mn is 2+. IR measurements showed low absorptions in the OH range and a much higher peak for H2O, indicating the presence of molecular water. B, N, and C were not detected on a microprobe equipped with a light element detector. Very small quantities of Li (39 ppm) and Be (43 ppm) were measured in a bulk sample that contained the contaminating minerals noted previously and significant contents of other elements were not evident during microprobe analyses. This mineral is a hydrous TiMnFe silicate; its XRD pattern was not matched using Panalytical's XPert HighScore Plus and the ICCD PDF-4 mineral (2011) data set. The chemical composition has some gross similarities to that of hydroastrophyllite, but the powder patterns are quite different. The author is amenable to suggestions as to how the unit cell dimensions might be determined.