Neutron Diffraction Studies on Gold Crystals from Placer Deposits

COFFEE_KLATCH · Invited

Abstract

The single-crystal nature of large (centimeter scale) gold crystals from placer deposits in Venezuela, Russia and elsewhere had often been questioned. Testing whether those gold crystals are indeed single crystalline has been a challenge because sectioning crystals to expose their interiors is both undesirable and problematic in that cutting or grinding creates significant deformation. Because of the relatively small penetration depth, X-rays will test mainly the surface structure. While in most cases the X-ray diffraction patterns on such crystal are inconsistent with single-crystal patterns, it has been hypothesized that surfaces may be damaged due to cold working as a result of mechanical distortion associated with stream transport. Unlike X-rays, neutrons can penetrate deep into the bulk of a material. Our neutron-diffraction data on selected specimens confirmed the single-crystalline nature of some of the crystals from Venezuela, while the Russian crystals were found to be cast imitations.

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Authors

  • Andrew Polemi

    Utah State University, Brigham Young University, University of Pennsylvania, Lawrence Livermore National Laboratory, Los Alamos National Laboratory, High Altitude Observatory, University of Colorado at Boulder, Massachutes Institute of Technology, Utah Valley University, University of New Hampshire, Applied Physics Laboratory, Johns Hopkins University, University of Montana, Southwest Research Institute, University of Southern California, Lockheed Martin Advanced Technology Center, University of Chicago, Massachusetts Institute of Technology, SciPrint.org, Centre National de la Recherche Scientifique, Colorado State University, V. Alecsandri College, Bacau, Romania, Colorado School of Mines, National Renewable Energy Laboratory, Utah State University, Department of Physics, Brigham Young University, Provo, Huntsman Cancer Institute, Brigham Young University - Idaho, University of Arizona, Florida State University, Weber State University, Brigham Young University - Provo, New Mexico State University, Colorado State University, Fort Collins, CO 80523