Next Article in Journal
Short-Range Stacking Disorder in Mixed-Layer Compounds: A HAADF STEM Study of Bastnäsite-Parisite Intergrowths
Next Article in Special Issue
Geometallurgical Study of a Gravity Recoverable Gold Orebody
Previous Article in Journal
PGE Production in Southern Africa, Part I: Production and Market Trends
Article Menu
Issue 11 (November) cover image

Export Article

Open AccessArticle
Minerals 2017, 7(11), 226; https://doi.org/10.3390/min7110226

Quantification and Prediction of Bulk Gold Fineness at Placer Gold Mines: A New Zealand Example

1
Department of geology, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
2
Waikaia Gold Ltd., Gore 9777, New Zealand
*
Author to whom correspondence should be addressed.
Received: 15 October 2017 / Revised: 5 November 2017 / Accepted: 16 November 2017 / Published: 19 November 2017
(This article belongs to the Special Issue Geometallurgy)
Full-Text   |   PDF [8258 KB, uploaded 19 November 2017]   |  

Abstract

This study documents the bulk Au fineness (Au parts per thousand) of the bullion from a placer gold mine in southern New Zealand. The compositions of doré bars produced approximately every 10 days over nearly three years is compared to the range of compositions of gold particles which have been extracted. Silver is the principal impurity in the gold, and the doré bars contained 2–3 wt % Ag over the period examined. At the scale of a typical individual 0.5 mm gold particle, there are three different types of gold: an Ag-bearing core (2–9 wt % Ag), a 10–50 µm wide Ag-poor rim (typically <1 wt % Ag), and micron scale overgrowth gold (0% Ag). The overgrowths are volumetrically negligible, and the average Ag content of a gold particle is controlled principally by the proportions of core and rim gold. The rims have been formed by recrystallisation of deformed core gold, with associated leaching of the Ag from the recrystallised gold. The volumetric proportion of cores has decreased with increasing flattening of gold particles, and highly flattened and folded flakes have little or no remnant cores. The bulk Au fineness of doré bars from the mine has decreased from ~980 to ~970 as the mine progressed upstream in a Pleistocene paleochannel because the upstream gold has been less flattened than the downstream gold. View Full-Text
Keywords: gold; silver; alluvial; recrystallisation; flake; grain gold; silver; alluvial; recrystallisation; flake; grain
Figures

Figure 1

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
SciFeed

Share & Cite This Article

MDPI and ACS Style

Craw, D.; McLachlan, C.; Negrini, M.; Becker, N. Quantification and Prediction of Bulk Gold Fineness at Placer Gold Mines: A New Zealand Example. Minerals 2017, 7, 226.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics

1

Comments

[Return to top]
Minerals EISSN 2075-163X Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top