Spectroscopic and Magnetic Studies of Ferric lron Hydroxy Sulfates: the Series Fe(OH)SO4nH2O and the Jarosites

George R. Rossman
 Division of Geological and Planetary Sciences
California Institute of Technology
Pasadena, CA  91125

Abstract

Optical and infrared absorption and magnetic susceptibility data are reported for the ferric iron hydroxy sulfate minerals and compounds: basic iron sulfate, Fe(OH)SO4; butlerite, Fe(OH)SO42H2O; parabutlerite, Fe(OH)SO42H2O;  fibroferrite, Fe(OH)SO45H2O; jarosite, KFe3(SO4)2(OH)6; and stewartite, MnFe2(H2O)6(OH)2(PO4)2. The relationships among intensity of color, indices of  refraction, pleochroism, antiferromagnetic interaction among Fe3+ ions, and structure are discussed for 7A corner-linked chain structures and the two-dimensional Fe3+ sheets of the jarosites, For all of these compounds the greatest intensity of the Fe3+ absorption bands and the highest refractive index occur when the vibration direction of the incident light is aligned with the cation chains or in the plane of the jarosite sheets. The ligand-field absorption band intensities of all of these compounds are enhanced up to two orders of magnitude above what they are in magnetically dilute compounds.

Magnetics
Magnetic susceptibility of the iron hydroxy sulphates and chromates



last updated: 23-Jul-2023