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Estimating mineralogy in bulk samples

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conference contribution
posted on 2023-05-23, 12:05 authored by Ronald BerryRonald Berry, Julie HuntJulie Hunt, McKnight, SW
This report looks at two ways to estimate the bulk mineralogy of the rocks for assay intervals. The aim is to find an efficient indicator of the most common minerals in the rock. Phase (modal) analysis has traditionally been done using visual methods such as point counting and image analysis. A modern version of this process is the X-ray point counting routine using the SEM-EDS based software. These methods are too slow and expensive for routine analysis of bulk sample mineralogy at the normal assay spacing. Two sources of data were considered that provide information that can be used to determine the mineral abundance in assay samples. The most widely applied method is (semi-) quantitative X-ray diffraction (QXRD). The QXRD method is most applicable to major minerals and has limited application to minerals at low abundance. The nominal detection limit is 0.5%. Values below 5% have large errors. A second, less common, method is calculation of mineralogy from chemical assay data. Conversion of chemical analyses to mineralogical analyses depends on the unique chemical composition of each mineral. Elements only found in one mineral are easily accounted for, but many compositions are ambiguous. Deciding on the actual mineralogy is not simple. Recalculation of mineral mode from chemical analyses is more accurate than QXRD when the correct minerals, and mineral compositions, are known. Where only a few QXRD analyses are available they can be used to setup a standard for calculation of mineralogy from assay data. We found linear programming works well in this environment. The best results are obtained when both H2O and CO2 are directly measured. LOI should be included if these are not available. Where both QXRD and chemical analysis are available for all samples, the best results are obtained using the least squared method to merge the datasets assuming QXRD errors have much higher analytical errors than chemical assays. The combined method provides more robust results because the high abundance minerals are controlled by the QXRD measurements while the chemical assays improve the precision for low abundance minerals.

Funding

Australian Research Council

AMIRA International Ltd

ARC C of E Industry Partner $ to be allocated

Anglo American Exploration Philippines Inc

AngloGold Ashanti Australia Limited

Australian National University

BHP Billiton Ltd

Barrick (Australia Pacific) PTY Limited

CSIRO Earth Science & Resource Engineering

Mineral Resources Tasmania

Minerals Council of Australia

Newcrest Mining Limited

Newmont Australia Ltd

Oz Minerals Australia Limited

Rio Tinto Exploration

St Barbara Limited

Teck Cominco Limited

University of Melbourne

University of Queensland

Zinifex Australia Ltd

History

Publication title

Proceedings of the 1st International Geometallurgy Conference (GeoMet 2011)

Editors

S Dominy

Pagination

153-156

ISBN

9781921522499

Department/School

School of Natural Sciences

Publisher

Australasian Institute of Mining and Metallurgy

Place of publication

Burwood, VIC, Australia

Event title

1st International Geometallurgy Conference (GeoMet 2011)

Event Venue

Brisbane

Date of Event (Start Date)

2011-09-05

Date of Event (End Date)

2011-09-07

Rights statement

Copyright the author

Repository Status

  • Open

Socio-economic Objectives

Expanding knowledge in the earth sciences

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    University Of Tasmania

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