The crystal structure and chemistry of natural giniite and implications for Mars

1Christopher T. Adcock,1Elisabeth M. Hausrath,2Elizabeth B. Rampe,3Hexiong Yang,3Robert T. Downs
American Mineralogist 108, 430-438Link to Article []
1Department of Geoscience, University of Nevada, Las Vegas, 4505 S. Maryland Parkway, Las Vegas, Nevada 89154-4010, U.S.A.
2NASA Johnson Space Center, 2101 E NASA Parkway, Houston, Texas 77058, U.S.A. 3
Department of Geosciences, University of Arizona, 1040 East 4th Street, Tucson, Arizona 85721-0077, U.S.A.
Copyright: The Mineralogical Society of America

Investigations of planetary processes using phosphate minerals often focus on igneous, recrystallized, or potentially metasomatized minerals, likely as a result of the minerals commonly available for
study within meteorites and lunar samples. However, Mars is a relatively phosphorus-rich planet and
possesses abundant evidence of past aqueous surface interactions. Therefore, secondary phosphate
phases may be important on the martian surface. Giniite [Fe2+Fe4
3+(PO4)4(OH)2·2H2O] is a secondary
phosphate mineral that has been suggested as a potentially significant phase at locations in Gusev Crater
and Meridiani Planum on Mars. Although relatively rare as a natural mineral on Earth, giniite has gained
attention as an important mineral in industry and technology, especially the lithium battery industry,
and the ferrian version of the mineral is often synthesized. This suggests giniite may be important as
an in situ resource utilization (ISRU) target for future extended human missions to Mars. Despite this,
there are few data available on the natural mineral and the last characterization of the structure was
over 40 years ago. There has also been confusion in the literature as to whether giniite is orthorhombic
or monoclinic. In this work we revisit and document the chemistry and crystal structure of natural
giniite from the type locality at the Sandamab pegmatite in Namibia using updated techniques. Our
results refine and update what was previously known regarding the structure and chemistry of giniite
and support the potential of the mineral as a possible martian scientific and resource target for further
study to aid future missions


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