A.E. Bence E.J. Dwornik J. R. Clark J. J. Papike M. Ross 1970 <p><span id="_mce_caret" data-mce-bogus="1" data-mce-type="format-caret"><span>Single-crystal x-ray diffraction, microprobe, optical and electron optical examinations of clinopyroxenes from Apollo 11 lunar samples 10003, 10047, 10050, and 10084 show that generally the crystals are composed of (001) augite-pigeonite intergrowths in varying ratios. Transmission electron micrographs reveal abundant exsolution lamellae, many only 60 Å thick. In addition to the phase inhomogeneities, primary chemical inhomogeneities are clearly demonstrated. There are reciprocal relationships between calcium and iron and between Ti</span>⁴⁺<span>&nbsp;+ 2Al and&nbsp;</span><i>R</i>²⁺<span>&nbsp;+ 2Si. Our evidence suggests that a chemically inhomogeneous subcalcic&nbsp;</span><i>C</i><span>2/</span><i>c</i><span>&nbsp;augite was the only primary pyroxene from which pigeonite later exsolved.</span></span></p> application/pdf 10.1126/science.167.3918.628 en American Association for the Advancement of Science Lunar clinopyroxenes: Chemical composition, structural state, and texture article