Performance of Sample Preparation for Determination of Gold in Samples of Geological Origin. Issue 3 (7th July 2019)

• Record Type: Journal Article
• Authors: Daniel, Lou; Clarke, Brenton R.; Parsons, Drew F.
• Is Part Of: Geostandards and geoanalytical research. Volume 43:Issue 3(2019)
• Page Start: 435
• Page End: 452
• Publication Date: 2019-07-07
• Subjects: gold ore -- statistical models -- sample preparation -- homogeneity -- geochemical analysis; Analytical geochemistry -- Periodicals; Géochimie analytique -- Périodiques; 551.9
• DOI: 10.1111/ggr.12278
• Languages: English
• ISSNs: 1639-4488

Abstract

Abstract : We investigate the performance of sample preparation of gold ores using vibratory (bowl, ring and puck type) mills in common use in mineral analytical laboratories. The main criteria for effective grinding are using reduced grinding charge masses ≤ ca . 50% of nominal bowl capacity and using a grinding aid to prevent caking. We show that gold particles of millimetre scale can be comminuted to ≤ 100 µm by grinding in silica flour, bauxite, synthetic carborundum, or mixtures of silica and these materials using times of up to 5 min and that 95% < 50 µm is achievable with extended grinding. This suggests that modified grinding techniques can be used to make sample masses ≤ 5 g viable for routine determination of gold in geological samples. We also demonstrate homogenisation of a gold‐bearing copper sulfide mineral flotation concentrate alone and in mixtures with silica by extended grinding at reduced charge masses. To support this work, we develop a convenient new benchmark of gold ore sample preparation performance ' G ', an apparent maximum gold particle size interpolated from replicate analytical variance in order to overcome the limitations of laborious sieve fraction analysis of gold particle size. We show useful agreement between G and sieve fraction analysis of gold particle size in samples and test the viability of G experimentally and by analysis of literature data. Abstract : Key Points A maximum gold particle size G in samples is estimated using the variance in replicate analyses. G is used here to monitor the progress of grinding initially 1 mm diameter gold particles in silica flour. The uncertainty in G decreases as more ( n ) replicates are used from 20 available analyses.