Major and minor element composition is reported for a Li–Fe mica (1M) occurring in topaz greisen of Precambrian age in southeastern Missouri, U.S.A. The Missouri zinnwaldite is high in MnO (2.44 wt%) and MgO (0.85 wt%) and is characterized by a 0.94 ion octahedral vacancy which places it nearly midway between the trioctahedral and dioctahedral states. The vacancies occur in the large-ion sites of the octahedral sheet and are regarded as the result of both octahedral and tetrahedral substitutions. Plotting of refractive indices against compositional variables confirms the unusual compositional nature of the Missouri zinnwaldite which resembles members of the zinnwaldite–masutomilite series described in Japan.

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A unique achondrite (ALHA77005) found by the joint U. S.-Japan team in Allan Hills, Antarctica is composed of olivine, pyroxenes, maskelynite, chromite, Ca-phosphate. The first occurrence of a three-pyroxene assemblage (orthopyroxene+pigeonite+augite) in meteorites is reported. The detailed chemistries and distribution of each phase indicate that the chemistries of the initial equilibrated assemblage are mostly preserved, but are partly modified by some processes related to shock events. A minor chemical zoning is observed from low-Ca pyroxene towards pigeonite. The orthopyroxene-like phase gives the X-ray diffraction pattern of pigeonite. Three kinds of pyroxene geothermometers developed by Ishii (Ishii et al., 1976) have been applied to this meteorite and the equilibrated ordinary chondrites. The estimated temperatures indicate that the initial equilibrated temperature of ALHA77005 (∼1160°C) is considerably higher than those of the ordinary chondrites (925°C–1010°C).

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Theoretical morphologies of α- and β-monoclinic selenium are derived based on Donnay-Harker’s law and Hartman-Perdok method (PBC analysis). In the case of PBC analysis, both Hartman’s point molecule treatment and a newly proposed detailed treatment are applied, which gave different morphologies. Crystals of α-monoclinic selenium are grown with varying evaporation rates from supersaturated solutions of carbon disulphide by slow evaporation method, and their morphologies are compared with the theoretical morphologies. Variations of crystal habits and surface microtopographs depending on the evaporation rates are analysed using the theoretically derived morphologies. It is found that the theoretical morphology derived by PBC method using the new “detailed treatment” agrees most well with the observed morphology.

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