Abstract

Bidirectional reflection spectra are presented from 0.35 to 2.5 mu m for a suite of ultramafic rocks collected from chromium-rich areas in southwestern Oregon and northwestern California. Features due to the presence of chromium are entirely absent from these spectra. However, the massive chromite samples are distinguishable from all others on the basis of spectral features produced by absorptions in ferrous ions located in unique tetrahedral sites afforded by the chromite spinel structure. Chromite samples are also distinguishable by their lack of specific absorption near 1.0 mu m, normally caused by ferrous ions located in octahedral sites; absorption in the 1.0 mu m region is the typical situation found in ultramafic and mafic rocks. The potential usefulness for remote-sensing purposes of this unusual spectral regime is suggested.

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