Uranium estimation studies on muscovites occurring as pegmatites in the Bhilwara area, Rajasthan State (India) give an evidence of second-phase intrusions of uranium in the mica matrix. The uranium content of mica varies from 10⁻¹⁰ atom/atom to 10⁻⁵ atom/atom. The mean fission track age for this region was found to be 1069±51 m. y. The pegmatites are of Precambrian origin but the uranium inclusions belong to a much later stage in the geothermal history of the samples.

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A systematics has been given of pyroxenoid structures based on a symbolism that describes configuration of octahedral bands, the variation of which characterizes structure types. Types of octahedral bands of pyroxenoids can be classified into two categories, thereby defining two structural series of pyroxenoids; one has been denoted by w–p (wollastonite–pyroxene) series, and the other p–p (pectolite–pyroxene) series. Basic differences in crystal structure and chemistry between these series are compared. In terms of the characteristics of structural units, each consisting of one octahedral band and a pair of silicate chains, it has been further shown that the triclinic symmetry of pyroxenoids is in principle an inherent nature for pyroxenoids.

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The crystal structure of natural cuspidine (Ca₄(F, OH)₂Si₂O₇) has been refined by full-matrix least-squares method to an R value of 0.042 using 1923 reflections. The crystal is monoclinic, P2₁⁄a, with a=10.906(5)Å b=10.521(6)Å, c=7.518(3)Å, β=109.30(3)°, Z=4. The structure originally determined by Smirnova et al. (1955) is basically correct. Cuspidine is a sorosilicate, in which Si₂O₇ groups are elongated parallel to the a-axis. The distances of bridging bonds Si–O are significantly longer than those of non-bridging bonds. The calcium atoms which connect these Si₂O₇ groups have six, seven and eight nearest neighbours of oxygen atoms, although Smirnova et al. considered that all calcium atoms were six coordinated. These calcium polyhedra form the columns and these columns are linked to form three-dimensional networks.

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