Analysis of Gold in Mineral Ores based on a Newly-built Portable Handheld LIBS System

Abstract

Conventional gold exploration and analysis techniques are often expensive, time-consuming, and limited in quantification accuracy. In this study, we developed a portable handheld LIBS system (PH-LIBS) for qualitative and quantitative analysis of gold in ore samples. The overall system weighs less than 2.5 kg, making it suitable for portable applications. This system consists of a pulsed laser, a customized spectrometer, a compact tablet computer as the central controller, and optical fibers. Seven certified gold ore standard materials with gold concentrations ranging from 0.35 to 160 g/t were analyzed with the PH-LIBS. A univariate quadratic regression model was established using the Au emission line at 199.7 nm. While this model successfully captured the linear response trend typical of high-grade samples (achieving an RMSE of 18.32 g/t and an MAE of 12.55 g/t), its quantitative resolution was limited for low-grade ores due to matrix effects. To address this limitation, a multivariate random forest (RF) model was developed as a complementary qualitative screening tool to categorize ore samples into discrete grades. The model achieved an overall accuracy of 81.82% on the validation set. Specifically, it yielded a precision of 0.90 for high-grade classification and a recall of 1.00 for low-grade classification. In addition, the instrument’s effective experimental limit of detection (LOD) for gold in ore was determined to be 13.3 g/t. Compared to conventional laboratory methods, the handheld LIBS system offers distinct practical advantages, including portability, real-time detection, and rapid semi-quantitative feedback. Consequently, it serves as a promising tool for the in situ characterization of Au-bearing ores during field exploration. Furthermore, this analytical method could be extended to other LIBS-detectable elements, subject to dedicated calibration and validation.