How Are Spectroscopy Techniques Used In Mining?

Introduction

The mining industry is a critical sector that drives global economies, providing essential materials for various industries. However, it faces significant challenges, including environmental impact, resource depletion, and the need for technological advancements. Efficient and accurate mineral exploration and extraction are paramount to overcoming these challenges. Spectroscopy emerges as a powerful analytical tool in this context, offering non-destructive testing and precise identification of minerals, which enhances decision-making and reduces environmental impact. This technique is revolutionizing the way the mining industry operates, leading to more sustainable practices.

Figure 1: The mining industry plays a significant role in the world economy.

Method

Spectroscopy techniques are widely used in the mining industry for various purposes, including exploration, ore analysis, and environmental monitoring. Here are some key spectroscopy methods used in mining:

1. Laser-Induced Breakdown Spectroscopy (LIBS): Utilizes a high-powered laser to create plasma from the sample, analyzing the emitted light to determine elemental composition.
2. Visible-Near Infrared (VNIR) and Short-Wave Infrared (SWIR) Spectroscopy: Measures the absorption of visible and short-wave infrared light to identify minerals and their properties.
3. Mid-Infrared Reflectance Spectroscopy: Analyzes the reflectance of mid-infrared light to provide information about mineral composition and structure.
4. Hyperspectral Imaging (HSI): Captures a wide range of wavelengths to create detailed images of mineral samples, allowing for precise identification and mapping of minerals
5. Field Spectroscopy: Portable spectroscopy tools used directly in the field for real-time analysis of mineral samples.
6. Atomic Absorption Spectroscopy (AAS): Measures the concentration of elements by analyzing the light absorbed by atoms in a sample, commonly used for detecting metals in ores.
7. Atomic Emission Spectroscopy (AES): Excites atoms in a sample and measures the emitted light to identify and quantify elements.
8. Raman Spectroscopy: Uses the scattering of monochromatic light to provide information about molecular vibrations and crystal structures, useful for identifying minerals and their chemical composition.
    

Application

Spectroscopy techniques are extensively applied in the mining industry for various purposes, including exploration, ore analysis, and environmental monitoring. Here are some key applications:

1. Mineral Exploration: Spectroscopy methods like Hyperspectral Imaging (HSI) and Near-Infrared Spectroscopy (NIR) are used to identify and map minerals based on their spectral signatures. This helps geologists locate mineral deposits more efficiently.
2. Ore Analysis: Techniques such as Laser-Induced Breakdown Spectroscopy (LIBS) and Atomic Absorption Spectroscopy (AAS) are employed to determine the elemental composition of ore samples. This information is crucial for assessing the quality and value of the ore.
3. Environmental Monitoring: Spectroscopy can detect and quantify contaminants from mining operations, helping to mitigate environmental impacts. For example, Raman Spectroscopy can identify hazardous substances in mine tailings.
4. Process Control: In mining operations, spectroscopy is used for real-time monitoring of processes LIBS can provide rapid, in-situ analysis, allowing for adjustments in processing to optimize recovery rates and reduce costs.
5. Quality Control: Spectroscopy ensures the consistency and quality of mined materials Atomic Emission Spectroscopy (AES) is used to verify the purity of metals and detect impurities that could affect the final product

Result

A specific application uses the LIBS spectrophotometry method in the analysis of mineral samples. Two drill core samples were provided for the analysis of the mineral composition inside. One sample is thought to contain gold and the other contains platinum and palladium. Figure 2 shows two sectioned drill core samples with delimited LIBS scanning areas marked by green rectangles.

Figure 2: Two mineral samples from the drill core were provided for composition survey using the LIBS method. Sample a contains gold, sample b contains platinum.
Table 1: Peak emission wavelength of some elements.

Table 1 lists the elemental emission lines used in the LIBS (Laser-Induced Breakdown Spectroscopy) analysis. Each element has a specific wavelength (in nanometers) at which it emits light when excited by the laser. This information is crucial for identifying and quantifying the elements present in the samples. In the table, we can see that gold has a peak emission wavelength at 267.59nm, silver at 328.07nm, platinum at 306.47nm and palladium at 340.52nm.

Figure 3: LIBS spectrum of suspected gold-containing mineral samples. The spectrum shows the peaks of the elements silver and silicon.

Figure 3 shows a LIBS spectrum for a pixel rich in gold and silver on mineral samples figure 2a. The spectrum displays the emission lines corresponding to the elements present in the sample, allowing for the identification and quantification of these elements. This helps in mapping the distribution of precious metals within the sample.

Figure 4: The LIBS spectrum of the mineral sample Figure 2b suspected to contain platinum. We can see the characteristic peak wavelengths of the elements platinum, palladium, and nickel.

Figure 4 in the paper shows a LIBS spectrum for a pixel rich in nickel, palladium, and platinum. This spectrum is part of the analysis of a drill core sample from figure 2b. The spectrum highlights the emission lines of these elements, indicating their presence and relative abundance in the sample. 

Measurement system

There are many spectroscopic methods that can be applied in the field of mining, followed by a variety of measurement systems corresponding to each different method. In this article, we would like to introduce a measurement system from Ocean insight that is suitable for the LIBS method.

Figure 5: HR2000+ spectrometer.

The Ocean HR2000+ spectrometer is a high-resolution device designed for the mining industry, utilizing the Laser-Induced Breakdown Spectroscopy (LIBS) method for precise material analysis. It boasts a high-sensitivity 2048-element CCD array detector, offering an optical resolution between 0.035 to 6.8 nm (FWHM). This makes it ideal for monitoring fast reactions and analyzing a wide range of materials with high accuracy. The HR2000+ is equipped with a variety of optics, including 14 gratings and 6 slit widths, allowing for customization according to specific application needs.

Figure 6: Ocean insight laser source

The Ocean 523nm laser source is an innovative tool designed for the mining industry, particularly for applications using the Laser-Induced Breakdown Spectroscopy (LIBS) method. This high-power laser boasts a wavelength of 523nm and can deliver exceptional performance with its narrow spectral lines, ensuring precise elemental analysis in various materials. The integrated laser driver is meticulously engineered to provide stable and reliable power, essential for the demanding conditions of mining operations. With its robust construction and advanced specifications, the Ocean 523nm laser source is an indispensable asset for enhancing efficiency and accuracy in mineral exploration and extraction processes. For detailed specifications and operational guidance, referring to the product's official documentation is recommended.