Gahnite in the metamorphosed stratiform massive sulfide deposits of the mineral district, Virginia, U.S.A.
This report describes the examination and analysis of 580 polished sections and 50 thin sections from located samples and diamond drill cores that penetrated the mineralized zones and associated host rocks of four of the stratiform sulfide deposits--Cofer, Arminius, Sulphur, and Julia--of the Mineral District, Virginia. The polished sections were prepared and examined according to conventional techniques. Because many of the samples were orginally selected for an examination of the ore mineralogy, there was a strong bias of samples to represent mineralized zones rather than the surrounding strata. Chemical analyses of gahnites and associated sulfide and silicate minerals were performed on an electron microprobe using synthetic sulfides and well-characterized natural grains of the following as standards: gahnite, fayalite, norbergite, tephroite, rutile, albite, orthoclase, and anorthite. Unit cell dimensions were determined using an automated norelco diffractometer employing ni-filtered cuka-radiation and using caf2 as an internal standard. Reflectance measurements on the gahnite wereperformed at 460, 546, and 650 nm using a photometer with magnetite, galena, and pyrite reflectance standards calibrated against a primary zeiss reflectance standard.