Merumite; a complex assemblage of chromium minerals from Guyana
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Professional Paper↗
Geology topics
D.E. Appleman
Publications and source records attributed to D.E. Appleman.
Crystallography of some lunar plagioclases
Crystals of calcic bytownite from type B rocks have space group I1 with c ≈ 14 angstroms. Bytownite crystals from type A rocks are more sodic and have space group C1, c ≈ 7 angstroms. Cell parameters of eight bulk feldspar separates from crystalline rocks indicate that the range of angle gamma is about 23 times the standard error of measurement, and its value might be useful for estimation of composition. Cell parameters of seven ilmenites are close to those of pure FeTiO 3 .
Science↗
Bonding in eight ordered clinopyroxenes isostructural with diopside
Bond distances and angles in isostructural, ordered clinopyroxenes are compared for eight compositions, based on five new and three published crystal-structure refinements from X-ray diffraction data. Unit-cell parameters and configuration of the silicate chains are directly correlated with cation composition and distribution in the M2 and M1 sites.
Contributions to Mineralogy and Petrology↗
Crystal chemistry and structure refinement of five hydrated calcium borates
The crystal structures of the five known members of the series Ca 2 B 6 O 11 ·xH 2 O (x = 1, 5, 5, 7, 9, and 13) have been refined by full-matrix least-squares techniques, yielding bond distances and angles with standard errors of less than 0·01 Å and 0·5°, respectively. The results illustrate the crystal chemical principles that govern the structures of hydrated borate compounds. The importance of hydrogen bonding in the ferroelectric transition of colemanite is confirmed by more accurate proton assignments.
Journal of Inorganic and Nuclear Chemistry↗
Unit-cell dimensions of natural and synthetic scapolites
In natural scapolites the cell dimension a shows a regular increase from marialite to meionite composition, while c remains constant. Both a and c of synthetic meionite are larger than the corresponding dimensions of synthetic marialite. The cell volume of both natural and synthetic scapolites is a nearly linear function of composition. Variations in cell dimensions of scapolites may be caused by differences in structural state similar to those in plagioclase feldspars.
Science↗
Crystal structure refinement of reedmergnerite, the boron analog of albite
Ordering of boron in a feldspar crystallographic site T 1 (0) has been found in reedmergnerite, which has silicon-oxygen and sodium-oxygen distances comparable to those in isostructural low albite. If a simple ionic model is assumed, calculated bond strengths yield a considerable charge imbalance in reedmergnerite, an indication of the inadequacy of the model with respect to these complex structures and of the speculative nature of conclusions based on such a model.
Science↗