The mining industry is among the largest industrial sectors in the world. Mining operations are important as they provide the essential minerals humans need in their daily lives.


A pivotal process known as mineral processing occurs beneath the Earth's surface, wherein raw ores transform valuable concentrates. Ores are critically analyzed as they help optimize the mining operation.

Obtaining accurate and representative results in mining applications is contingent upon taking high-quality ore samples and carefully analyzing them. Experts select the various methods and technologies for ore analysis with the complete mining operation in mind.

Fire Assay Method for Ore Analysis: The Industry Standard

The fire-assay method is the industry standard for analyzing gold, silver, and platinum ores in mining. It involves three stages: smelting the ores with fluxes, isolating precious metals from metallic lead, and analyzing the obtained metals.

Finely ground ore is mixed with glass fluxes, litharge, and a carbon source in this process. The mixture is smelted in a ceramic crucible at temperatures ranging from 900 to 1100 °C for approximately an hour. The reduction in lead oxide leads to the formation of a lead button at the crucible bottom, collecting the precious metals.

The precious metals are isolated from the lead button using magnesium oxide or calcium oxide cupels in the cupellation process. These cupels absorb oxidized lead above its melting point (900-1000 °C).

During fire assay, added iron reacts with sulfur in the matte phase, causing lead to return to the metallic state. Adding iron is suitable for ensuring reliable results in the traditional fire assay procedure.

Wet Assay Ore Analysis Technique

Wet metal assay techniques involve transforming the "ore" into powder and thoroughly dissolving it in a liquid, typically an acid or a combination of acids. The presence of known metals is recognized by the peculiarities of the precipitate produced when a reagent is added to the solution.

If the mineral contains sulfur, arsenic, or other volatile substances (such as iron pyrites, copper pyrites, and galena), powdering and roasting it is recommended. This eliminates sulfur, leaving the metallic portions in oxide form for examination.

Certain minerals, like graphite, cinnabar, some oxides, sulfates, chlorides, and various silicates, are insoluble in acid. To facilitate the testing of these materials, approximately four times the weight of carbonate of soda can be added to the powdered mineral.

They can then be melted in a crucible, leaving the metallic portion in a condition to be dissolved by hydrochloric acid.

Total Reflection X-Ray Fluorescence Spectrometry for Elemental Analysis of Ores

Recently, total reflection X-Ray fluorescence (TXRF) spectrometry has been used for the elemental analysis of ores. This method is efficient in the determination of trace amounts of minerals.

A recent article published in Spectrochimica Acta Part B: Atomic Spectroscopy highlights the application of TXRF for elemental analysis in sulfur ores. The use of various ores, each with different elemental concentrations, aims to depict the effectiveness of TXRF.

A suspension was created to prepare samples for TXRF analysis using 5 mL of 1% Triton solution and 20 mg of fine powder with a median particle size below 10 µm.

Copper-nickel sulfide ores were analyzed using TXRF analysis after acid digestion and following the initial drying of the powder mixed with the gallium, internal standard. Sulfur concentrations were notably lower than reference values after acid digestion, while TXRF reliably determined sulfur in the suspension without acid digestion.

Strong correlations between TXRF and certified technique data were observed for iron, nickel, and copper in both suspensions and solutions post-digestion. While acid digestion slightly improved the accuracy of iron and copper determination, achieving a quantitative determination of trace elements in copper-nickel sulfide ores would necessitate matrix separation.

Gallium, germanium, and selenium are commonly used as internal standards in TXRF analysis. Both theoretical and experimental assessments highlighted the importance of thoroughly milling ore powders to achieve reproducible measurements.

The researchers emphasized the importance of maintaining a median particle size of less than 10 μm, as larger sizes hindered the reproducibility of the sample deposition process. For ore powders with low wettability, the team also recommended initially drying the powder mixed with a gallium solution to enhance internal standard distribution uniformity and improve reproducibility.

Automated Mineral Liberation Analysis Techniques for Rare Earth Minerals in Ores

Rare-earth elements (REEs) ore deposits are found in various geological settings and rock types. These include hydrothermal veins, stockworks, and sedimentary mineral placers containing REE ores. Chemical weathering can enrich REEs, especially in lateritic clays.

A recent article in the journal Minerals highlights the various techniques used by companies analyzing minerals present in ores. Experts use scanning electron microscopy (SEM) for surface analysis of ores.

The process of inductively coupled plasma mass spectrometry (ICP-MS) has proven successful in determining REEs in ores. ICP-MS is sometimes coupled with X-Ray fluorescence analysis to determine the concentration of different minerals.

Both techniques require powdered samples with small grain sizes (less than 2 micrometers), yet they do not provide information about particle sizes, mineral compositions, and interconnections.

Understanding particle-related aspects is crucial in the beneficiation of REE ores. Thus, researchers commonly employ non-destructive methods such as SEM with energy dispersive spectroscopy (EDS) and automated backscattered electron (BSE) image analysis, known as automated mineralogy.

Automated On-Belt Sampling and Analysis of Ores

Accurate chemical analysis is crucial for optimizing mining operations, resulting in improved extraction and better blending of mined materials. However, sending samples to distant laboratories introduces delays of hours to days. Developing an automatic system that can sample ores and perform analysis in a short time can accelerate the mining process.

Considering the time constraints, the new automated on-belt sampling and analysis technique is becoming popular in the industrial processing of ores. Rather than sending ores to a laboratory for sampling and analysis, this technique uses a cross-belt sampler, which directly collects the samples from a moving belt. The system can be tailored to meet relevant sampling and preparation standards.

Collected samples are then crushed to the required size, and the moisture content is measured and recorded to eliminate measurement bias. The prepared samples are then pressed and undergo chemical analysis in a fully automated process. The results are seamlessly integrated into the plant workflow and data management system.

Ore analysis is a crucial step in mining operations. A comprehensive and rapid ore analysis saves time, money, and effort and optimizes the mining process. With the recent developments in imaging and analysis techniques and the integration of artificial intelligence, a revolution in the field of ore analysis can be soon expected.