CRYSTAL-STRUCTURE OF PREHNITE FROM KOMIZA

The criystal structure of prehnite (Ca2(Al,Fe) (OH)2 [ Si3AlO10])from Komi\u17ea (Yugoslavia) has been refined in the space group P2cm (a=4,646(2) \u1fa, b= 5.491(3) \u1fa, c=18.52(3) \u1fa, Z=2). Si and Al showed a completely ordered distribution in the structure. The obtained Fe-Alsubstitution for the octahedral coordination is 17%. No monoclinic domains could be observed in the crystals. Laue photographs show that the splitting of the diffraction maxima in prehnite from Komi\u17ea is due to lattice rotation around the direction of the b axis

Authigenic mica in Early Miocene volcaniclastic rocks of the Macelj area, Hrvatsko Zagorje, Croatia

In the Early Miocene zeolitized volcanicalstic rocks from NW part of Hrvatsko zagorje green authigenic mica occurs in thin veins and coatings of glass shard vesicles. X-ray powder pattern with widened but still relatively sharp reflections is characteristic for 1M micas, with Fe-rich octahedral sheet. The observed value d(060) is 1.508 \uc5. IR spectrum is characterized by sharp absorption bands in the OH stretching region, with two strongest bands at 3580 cm-1 and 3600 cm-1 ascribed to Al-Fe3+ and Al-Mg cationic environment of the OH groups. Microprobe analyses revealed that this is an interlayer-deficient dioctahedral mica, with Al as dominant cation in octahedral sheet, viM3+>1.2, and low tetrahedral substitution, with quite peculiar chemical composition that does not correspond ideally to any member of the mica group

Rotating lattice single crystal architecture on the surface of glass

Defying the requirements of translational periodicity in 3D, rotation of the lattice orientation within an otherwise single crystal provides a new form of solid. Such rotating lattice single (RLS) crystals are found, but only as spherulitic grains too small for systematic characterization or practical application. Here we report a novel approach to fabricate RLS crystal lines and 2D layers of unlimited dimensions via a recently discovered solid-to-solid conversion process using a laser to heat a glass to its crystallization temperature but keeping it below the melting temperature. The proof-of-concept including key characteristics of RLS crystals is demonstrated using the example of Sb(2)S(3) crystals within the Sb-S-I model glass system for which the rotation rate depends on the direction of laser scanning relative to the orientation of initially formed seed. Lattice rotation in this new mode of crystal growth occurs upon crystallization through a well-organized dislocation/disclination structure introduced at the glass/crystal interface. Implications of RLS growth on biomineralization and spherulitic crystal growth are noted