Jaszczak et al. 1 MICRO- AND NANO-SCALE GRAPHITE CONES AND TUBES FROM HACKMAN
Several unusual forms of natural graphite from an alkaline pegmatite that crosscuts rischorrite in the Hackman Valley, Khibiny Massif, Kola Peninsula, Russia are described. The graphite occurs macroscopically in two forms: as spherical aggregates up to 2 cm in diameter of friable, radially-aligned f...
| Main Authors: | , , , , |
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.531.3761 http://www.phy.mtu.edu/~jaszczak/Kola/kola-graphite-ppt.pdf |
| Summary: | Several unusual forms of natural graphite from an alkaline pegmatite that crosscuts rischorrite in the Hackman Valley, Khibiny Massif, Kola Peninsula, Russia are described. The graphite occurs macroscopically in two forms: as spherical aggregates up to 2 cm in diameter of friable, radially-aligned fibers ~20 µm in cross section, and as fine-grained surface coatings in cavities covering aegirine, strontian fluorapatite and K-feldspar. Optical microscopy and field emission scanning electron microscopy (FESEM) show that the fibers are actually hollow channels whose walls are composed of tabular graphite crystals greatly elongated in the direction of the fiber axis and with their basal planes oriented parallel to the channel walls. Inside and among the channels occur rolled graphitic structures (RGS): scrolls, tubes, and cones, up to 2 µm in diameter and up to 15 µm in length. The fine-grained graphite coatings on the surfaces of cavities, on the other hand, consist almost solely of micro- and nano-scale RGS. The largest of the RGS are hollow scrolls, with the c-axis predominantly perpendicular to the scroll axis. These are usually cigar shaped but can also be more tubular. Conical RGS occur at the micro- and nano-scales. The nano-scale |
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