Relationships between unit-cell parameters and composition for rock-forming minerals on Earth, Mars, and other extraterrestrial bodies

• Published in: The American mineralogist Vol. 103; no. 6; pp. 848 - 856
• Main Authors: Morrison, Shaunna M, Downs, Robert T, Blake, David F, Prabhu, Anirudh, Eleish, Ahmed, Vaniman, David T, Ming, Douglas W, Rampe, Elizabeth B, Hazen, Robert M, Achilles, Cherie N, Treiman, Allan H, Yen, Albert S, Morris, Richard V, Bristow, Thomas F, Chipera, Steve J, Sarrazin, Philippe C, Fendrich, Kim V, Morookian, John Michael, Farmer, Jack D, Des Marais, David J, Craig, Patricia I
• Format: Journal Article
• Language: English
• Published: Washington Mineralogical Society of America 01.06.2018; Walter de Gruyter GmbH
• Subjects: achondrites; Algorithms; Alunite; Calcium; Chemical composition; CheMin; crystal chemistry; Curiosity (Mars rover); Curiosity Rover; Earth; extraterrestrial geology; Extraterrestrial materials; Extraterrestrial matter; feldspar group; Feldspars; framework silicates; Gale Crater; instruments; Iron; Jarosite; Magnesium; Magnetite; Mars; Mars craters; Mars Reconnaissance Orbiter; Mars rovers; Mars Science Laboratory; Martian meteorites; Martian Rocks and Minerals; Meteorites; Mineralogy; Minerals; nesosilicates; Olivine; olivine group; Orbiters; Organic chemistry; orthosilicates; Oxides; Parameters; Perspectives from Rovers; Plagioclase; planets; pyroxene; silicates; spinel; stony meteorites; sulfates; techniques; terrestrial planets; Unit cell; unit-cell parameters; X rays; X-ray analysis; X-ray diffraction; X-ray diffraction analysis; X-ray diffraction data
• DOI: 10.2138/am-2018-6123
• ISSN: 0003-004X

Mathematical relationships between unit-cell parameters and chemical composition were developed for selected mineral phases observed with the CheMin X-ray diffractometer onboard the Curiosity rover in Gale crater. This study presents algorithms for estimating the chemical composition of phases based solely on X-ray diffraction data. The mineral systems include plagioclase, alkali feldspar, Mg-Fe-Ca C2/c clinopyroxene, Mg-Fe-Ca P21/c clinopyroxene, Mg-Fe-Ca orthopyroxene, Mg-Fe olivine, magnetite, and other selected spinel oxides, and alunite-jarosite. These methods assume compositions of Na-Ca for plagioclase, K-Na for alkali feldspar, Mg-Fe-Ca for pyroxene, and Mg-Fe for olivine; however, some other minor elements may occur and their impact on measured unit-cell parameters is discussed. These crystal-chemical algorithms can be applied to material of any origin, whether that origin is Earth, Mars, an extraterrestrial body, or a laboratory.