AN SEM INVESTIGATION OF A NATIVE PLATINUM CRYSTAL FROM RUSSIA: INSIGHT INTO VARIATION, SOURCING AND COMPOSITIONAL PROBLEMS OF A HIGHLY COLLECTIBLE MINERAL AND IMPORTANT GEOLOGIC RESOURCE

Platinum is a metal that is vital to several modern industrial processes and environmental mitigation methods. For example, platinum is used as a catalyst in various chemical reactions, including: processing fertilizer for agricultural uses, catalytic converters to facilitate the complete combustion of hydrocarbons in exhaust systems, and implantable medical devices (i.e. pacemakers and defibrillators). The use of platinum in these scenarios is largely due to the resistance of the metal to corrosion. While macroscopic crystals of platinum are rare in the geological record, throughout Siberia there are known locales at which such examples of macroscopic platinum crystals can be found. Whether or not platinum crystals grow by classic growth, or by nanoparticle aggregation or other mechanisms is unclear. Scanning electron microscopy (SEM) work was conducted to assess if there are any textural indications of platinum crystal growth mechanisms. SEM results indicate that smooth well defined step – terrace textures are present with steps being approximately 1 to 3 micrometers in height and terraces being 1 to 25 micrometers in width. Elemental maps indicate complex intergrowths of silicates in portions of the crystal: Cr, Fe and Pb appear to be inherent to the platinum. Al and Ca are also detected and this is noted here as being unexpected owing to the 3+ charge and under fit size of the Al cation and 2+ charge of the Ca cation. Although impurities of Cr, Fe, and Pb are not unexpected in native Pt, Al and Ca are however, and may therefore exist as nanoscale inclusions. Minor to trace amounts of Si, Mg, Mn and O throughout the platinum crystal also supports the hypothesis of extensive nanoscale inclusions. These preliminary findings suggest that platinum crystals warrant further investigation with transmission electron microscopy and computed X-ray tomography. Limited data exists on other well-known platinum crystals from the Konder Massif, Russia. From SEM work, those platinum crystals are reported to be nearly pure platinum, unlike what has been preliminarily studied here. Results suggest a detailed survey of native platinum crystals is warranted in order to determine sources of crystals in collections, understand growth mechanisms and purity, and better constrain the geologic environments in which they occur.