Joaquinite: The Nature of its Water Content and the Questin of Four-Coordinated Ferrous Iron

Abstract

The polarized optical and infrared spectra of oriented crystals of joaquinite from San Benito County, California, have been obtained. Te infrared spectra ahve polarized absorption bands at 3561, 3500, and 1607 cm^-1, which are assigned to the vibratinos of crystallographically ordered molecular water in joaquinite. The optical spectra show features due to neodymium and divalent iron. The near infrared absroptions near 1000 and 2100 nm are discussed in terms of six-coordinated iron(II) rather than four-coordinated iron(II) proposed from X-ray structural studies. 

The infrared spectrum of joaquinite showing the water modes

Near-IR absorption spectrum of Joaquinite showing overtone and combination modes of water.