Recent Contributions and Modem Perspectives in XRD Studies of Minerals

Some exciting recent developments in the field of mineralogical crystallography are considered. The crystal Chemical phenomena (e.g. ionic ordering, polyhedral stacking variations, microtwinning, modulation), which accompany the formation of real structures, are discussed on the basis of structural studies of a large group of minerals, recently investigated in the Moscow State University. The new approaches used for their investigation allowed extending the Scientific ideas connected with: the composition and structure of the deep geospheres, structural classification of minerals, forms of concentration of Chemical elements in the Earth\u27s crust, further development of modular theory and other problems of modern structural mineralogy. The advantage of using synchrotron radiation opens the gate to a new branch of microgeochemistry (about 20% of known minerals lack structure determination, mainly because crystals are too small or imperfect for laboratory X-ray sources). Studies of the phase transitions of mantle minerals at high pressure and high temperature contribute to a better understanding of the composition, structure and geodynamics of the deep geospheres. A new model of the mantle, based on the most recent seismotomographic data and on the phase transition studies of mantle minerals, is reported. Several concentric bands are revealed in the mantle, although the previous model emphasized its subdivision only in two parts: upper and lower. New approaches to the XRD studies of ionic ordering, structural modulation and polyhedral stacking variations are discussed

Dmitry I. Mendeleev and his time

The history of the creation of Periodic table and of the Mendeleev’s discovery of Periodic Law is considered. The different approaches used by Mendeleev’s colleagues are discussed. The contribution of the Periodic system to the extension of the scientific ideas in geology and best of all in geochemistry and mineralogy is illustrated by the discovery of new chemical elements and by the isomorphic replacements in minerals. The details of uneasy history of Mendeleev’s nomination to the St. Petersburg Academy and for the Nobel Prize are given

New Approaches to the XRD Studies of Complicated Crystal Chemical Phenomena in Minerals

The crystal Chemical phenomena (e.g. polyhedral stacking variations, microtwinning, modulation, etc.), which accompany the formation of real structures, are considered on the basis of the most recent structural studies of a large group of silicate minerals and their synthetic analogues, e.g. raite, vuorijarvite, haiweeite and synthetic K4(NbO)2[Si8O21]. The new approaches used for their investigation allowed extension of the Scientific ideas connected with the structural systematics of minerals, the forms of concentration of Chemical elements in the Earth’s crust, further development of modular theory and with other problems of modern structural mineralog