Petrological and mineralogical research of primitive achondrite meteorite NWA 6704

Abstract

NWA 6704 is a unique achondrite. We performed a detailed petrological and mineralogical study of this meteorite based on optical microscopy, secondary electron microscopy, micro-Raman spectroscopy, and electron microprobe analysis. We identified olivine, low-Ca pyroxene, high-Ca pyroxene, plagioclase, chromite, awaruite, pentlandite, and heazlewoodite. These minerals are almost identical to those in NWA 6693, which has been thought as one of paired meteorites of NWA 6704 although K-rich plagioclase was not identified in NWA 6704. However, the major crystal structure of low-Ca pyroxene is different between NWA 6693 and NWA 6704. In the former, the major phase is low-Ca pigeonite.