THE MORPHOLOGY OF DIAMOND CRYSTALS FROM METAMORPHIC ROCKSстатья

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[1] Nadejdina E. D., Posukhova T. V. The morphology of diamond crystals from metamorphic rocks // Минералогический журнал. — 1990. — Vol. 12. — P. 3–64. Metamorphic diamond microcrystals were found in Kazakhstan and China [Xu et al,1992] and in residues from the thermochemical dissolution of garnet-biotite-kyanite and garnet-hornblende-biotite gneisses from Western Gneiss Region of Norway [Dobrzhinetskaya et al,1993]. They are very small(0,02-0,08mm) and have unusual forms. In metamorphic rocks we have not dodecahedra, there are very few octahedra. In this rocks we may see very interesting forms: skeletal and spheric, faced (antiskeletal) and edge rays, boxed and tabular forms and very unusual aggregate skeletal crystals, which are formed by coarse-layered blocks. The origin of metamorphic diamonds is a very difficult problem. There are many hypothesis according to this question. The comparison metamorphic crystals morphology with diamond from kimberlites shows, that they are very much differed,but some forms of metamorphic crystals are similar to artificial diamonds. The similarity between metamorphic and synthetic diamonds permit as to apply the growth theory to explanation the spetciphic of metamorphic diamond morphology. The similarity between real structure of small cubic nature diamonds and synthetic one, which were given during the spontaneous crystallization, means that they crystallized very quickly, during a short time at unequilibrium conditions at the low temperature and pressure from saturates solutions which were riche of impurities.

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