Exploration & Characterization

Elemental characterization and moisture content of coal

Elemental characterization of coal is fundamental in geology and mining for determining the chemical composition. Knowing the content of key elements such as carbon, hydrogen, sulfur, nitrogen, oxygen is crucial for resource valuation, and process control in extractive metallurgy.

The purpose is also to assess the fuel value and environmental impact of coal. Carbon and hydrogen directly influence the calorific value (energy content); sulfur contributes to SO₂ emissions on combustion and must be controlled. These parameters inform whether a coal meets specifications for power generation or steelmaking, and they help in resource grading and mine planning.

Instruments operate according to ASTM/ISO methods (e.g. ASTM D5373 and ISO 29541 for C, H, N in coal and ASTM D4239 / ISO 19579 for sulfur in coal). These standards ensure that the analyzers provide accurate, repeatable results in line with industry norms. For example, Eltra’s high-temperature CS-r analyzer yields sulfur results compliant with ISO 19579:2006 (Solid mineral fuels – Determination of sulfur by IR spectrometry) and ASTM D4239 (Standard Test Method for Sulfur in Coal and Coke).

Also moisture content in coal is quite important determination done by Thermogravimetric Analysis (TGA), where the mass loss observed upon controlled heating corresponds to the evaporation of inherent and surface water, following standard methods such as ASTM D7582 or ISO 11722.

Ultimate analysis standard methods on coal

Ultimate analysis of coal is standardized in both ISO and ASTM methods, sometimes referred to as “elemental analysis” or part of a coal’s “ultimate” properties. ASTM D5373 and ISO 29541 cover C, H, N by instrumental combustion; ASTM D4239 and ISO 19579 cover sulfur by high-temperature combustion/IR detection. Industry literature emphasizes the importance of these measurements for coal grading.

For instance, hydrogen content contributes to water formation during combustion, reducing usable heat, so it’s directly tied to coal’s effective calorific value. Measuring these elements precisely with analyzers like Eltra’s ensures that mining operations and coal buyers have reliable data on fuel quality.

Sulfur Determination for Mineral Grade Evaluation

Many base and precious metal ores, including copper, lead, and zinc, occur as sulfide minerals such as chalcopyrite (CuFeS₂), galena (PbS), and pyrite (FeS₂). Measuring sulfur content in these geological samples is a proven approach for mineral grade evaluation, as sulfur concentration typically correlates with sulfide abundance and therefore with potential metal yield. In copper mining, for example, sulfur determination provides an indirect but robust proxy for copper grade. Since chalcopyrite has a fixed Cu:S ratio, higher sulfur values indicate greater chalcopyrite content and, consequently, higher copper potential. This makes sulfur analysis a cost-effective and rapid tool for exploration campaigns, resource evaluation, and process optimization.

Accurate sulfur determination is performed with ELTRA’s CS-i carbon/sulfur analyzers, which employ high-temperature induction combustion (>2000 °C) in an oxygen atmosphere. The sulfur released as SO₂ is quantified by infrared detection, ensuring precise and reproducible results even for refractory sulfide minerals. The method accepts relatively large sample weights (200–300 mg), which improves representativity in heterogeneous ores. Standardized procedures—such as ISO 14869-1 for soils and ores, ASTM E1915 for metal-bearing ores, and analogs to ASTM D4239/ISO 19579 used in fuel analysis—support the reliability and comparability of results across laboratories and projects.

By converting sulfur percentages to approximate mineral or metal content using known stoichiometries, geologists gain a direct link between elemental analysis and economic grade. This makes sulfur determination with ELTRA’s CS-series analyzers an indispensable part of modern exploration, geometallurgy, and quality control workflows, bridging laboratory precision with real-world mining decisions.

Solutions Empowering Geology and Mining Laboratories

QATM’s precision preparation equipment is essential for advancing material studies in the fields of geology and mining. From mineralogical assessments to specialized planetary research, QATM offers the tools and techniques to deliver reliable, high-quality sample preparation for a broad range of geoscientific applications.

Applications in Mining and Mineral Analysis

Ore Mineral Intergrowth Analysis

Properly prepared thin sections are crucial for identifying mineral locking—where minerals are intergrown in ways that affect grinding and separation strategies in ore processing.

Reflected Light Microscopy & Electron Beam Analysis

Polished sections are required to study opaque minerals (such as sulfides and oxides) under reflected light. These same surfaces are also indispensable for quantitative assays via electron microprobe and automated mineralogy platforms like QEMSCAN.

Sample Integrity and Preparation Quality

Achieving a flawless, representative surface without microcracks is vital. QATM’s vacuum impregnation units and precision cutters ensure structural integrity and optimal preparation from the start.

Hardness and Wear-Related Studies

While not routine, microhardness or scratch testing on specific mineral phases can support research into grindability or wear behavior—areas where QATM’s hardness testing equipment provides precise, phase-specific insights.

Beyond Mining: Supporting Broader Geoscience Research

  • Paleontology: High-precision polishing for fossil examination and structural studies.
  • Meteoritics: Etching and polishing of iron meteorites to reveal Widmanstätten patterns, vital for classification and origin analysis.
  • Planetary Geology: Sample preparation of extraterrestrial materials where surface finish and integrity are critical for high-resolution analysis.

Polished Mounts for Mineral and Ore Analysis

Preparing polished mounts (also known as polished blocks) is a critical step in the analysis of rock, ore, and coal specimens. These mounts enable high-precision observations under reflected light microscopy and are indispensable in various electron beam analyses such as SEM (Scanning Electron Microscopy) and electron microprobe work. Unlike thin sections—which are translucent slices mounted on glass—polished blocks are thicker briquettes or pieces of material featuring a flat, mirror-like surface. They are especially suitable for studying opaque mineral phases that are otherwise invisible in transmitted light.

Observation of Opaque Minerals

Many ore minerals, including pyrite, chalcopyrite, and galena, are opaque. These must be examined in reflected light using a polished surface to reveal key features such as mineralogy, grain boundaries, exsolution textures, and microfractures.

Quantitative Automated Mineralogy

Systems like QEMSCAN or MLA use SEM/EDS to scan polished surfaces for mapping mineral compositions. These are widely used in mining operations to evaluate mineral liberation and associations, crucial for optimizing processing techniques.

Electron Microprobe Analysis

A polished, smooth surface ensures accurate X-ray detection during microprobe analyses. This is essential for studying zonation, identifying tiny mineral inclusions, and determining detailed chemical compositions.

 

Coal Rank and Petrographic Analysis

In coal studies, polished pellets are used to measure the reflectance of vitrinite macerals—an essential parameter for classifying coal rank and assessing suitability for coke production.

Fluid Inclusion Microthermometry

For analyzing fluid inclusions, doubly-polished thick sections (polished on both sides) are required. High-quality polishing is crucial to clearly observe tiny inclusions, especially in quartz and ore minerals.

Standards and Best Practices

General Metallography: ASTM E3 outlines standard practices for metallographic sample preparation.

ISO 7404-2 and ASTM D2797 specify preparation methods for coal pellets, including the use of aluminum oxide for final polishing to prevent alteration of reflectance measurements.

Polished mounts are indispensable tools in both academic and industrial geoscience. They bridge the gap between observational and analytical methods, offering a reliable platform for both qualitative and quantitative analysis. 

QATM Equipment in Geology and Mining

For instance, in mining:

  • Proper thin sections of ore can reveal mineral locking (which minerals are intergrown, affecting grind and separation strategies).
  • Polished sections are required for reflected light microscopy to identify opaque ore minerals (like sulfides, oxides) and to do assays by electron microprobe or automated mineralogy (e.g., QEMSCAN).
  • Ensuring sample integrity (no cracks, representative surface) is essential; QATM’s vacuum impregnation and precision cutting help in this.
  • Hardness testing or scratch testing might be applied to minerals to correlate with grindability or wear (though not routine, research may require microhardness of specific phases).
  • Furthermore, geologists may use similar prep for paleontology (e.g., polishing fossils), meteoritics (etching iron meteorites to reveal Widmanstätten patterns), or planetary geology samples.

 

Preserving Petrographic Precision in Coal Oxidation Studies

Understanding coal weathering and oxidation is essential for accurate petrographic analysis and vitrinite reflectance measurement. As highlighted in recent studies, surface alterations during oxidation can significantly affect coal classification and usage potential. QATM's advanced sample preparation solutions—ranging from precision cutting to automated polishing—ensure optimal surface quality for reliable analysis under reflected light microscopy. Whether you're studying natural weathering or simulating oxidation in the lab, QATM systems provide the consistency and control needed for reproducible results. Trust QATM to support your research in coal behavior and carbon material integrity.

Vacuum Impregnation of Porous Geological Samples

Stabilizing and reinforcing porous, fissile, or particulate geological samples by impregnating them with resin under vacuum before cutting or polishing. Many geological materials – e.g., highly porous sandstones, loosely consolidated soils, coal, or mineral concentrates – can crumble or lose pieces during preparation. Vacuum impregnation fills the pores and cracks with epoxy, providing mechanical support and preventing the loss of material (or bubble formation) when sectioning and polishing.

Why it is performed:

  • To preserve sample integrity: A friable ore with vugs or a weathered rock with clay-filled fractures might fall apart if cut dry. Impregnation ensures the sample holds together and the internal structure is preserved for microscopy. Without impregnation, pores might collapse or grains detach, which would ruin a thin section or polished mount.
  • To achieve good polish and representation: Open pores can lead to dragging of softer material into holes during polishing, causing relief and preventing a flat surface. Filling pores with resin provides a continuous surface that can be polished flat – critical for quantitative image analysis or electron microprobe work (where holes would cause beam artifacts).
  • In preparation of powdered samples into a solid mount: Sometimes geologists want to examine a powdered sample (like heavy mineral separates or tailings). These can be mixed with resin and cast into a solid plug under vacuum to remove air and ensure particles are locked in place.
  • Under vacuum, resin penetrates even fine pores (capillary action alone might not fill tiny cracks due to trapped air). This yields a stronger, void-free mount.

Preparation of Petrographic Thin Sections

The creation of standard thin sections—rock or mineral slices approximately 30 µm thick mounted on glass slides—is essential for examination under transmitted light or polarizing microscopes. As a cornerstone technique in geology, thin sections reveal the mineral composition, microstructures, and textures of rocks in fine detail. QATM equipment supports every stage of this process: from precision cutting of the initial slice, through controlled grinding to achieve uniform thickness, to optional polishing on one or both sides for enhanced optical clarity.

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Why Thins Section?

  • Mineralogical analysis: Many minerals are translucent and can only be properly identified in thin section using their optical properties (birefringence, refractive index, extinction angle, etc.).
  • Textural interpretation: Thin sections allow geologists to see grain relationships – crystal shapes, size distribution, fabric (alignment), and features like zoning or alteration.
  • Geological history: From thin sections, one can infer rock genesis – e.g., a metamorphic rock’s foliation, a volcanic rock’s phenocryst and groundmass arrangement, or a sedimentary rock’s cement and porosity.
  • In mining, thin sections of ore can show how ore minerals and gangue are intergrown, which informs grinding and separation strategies (though reflected light polished sections are more common for opaque ore minerals, thin sections still show silicates and can be stained for carbonates, etc.).
  • It’s also standard for academic research, teaching (student petrography labs), and for specialized analyses like fluid inclusion studies (which require thick sections or doubly polished sections).

QATM provides specific tools: a thin section saw (or a universal cutter that can thin), a thin section press (to ensure bubble-free contact of rock to slide), and a line of grinding discs (diamond cups) and polishing cloths.

Microhardness Testing of Minerals and Rocks Precise Measurement of Mineral and Phase Hardness in Geosciences

Micro-indentation hardness testing—using techniques such as Vickers or Knoop under low loads—is a powerful method for evaluating the hardness of individual mineral grains and phases in geological specimens. While commonly used in metallurgy, this technique is equally valuable in the geosciences. QATM microhardness testers, originally developed under the Qness brand, offer precise, reliable measurement solutions that extend beyond metals to polished rock, ore, coal, and planetary samples.

Key Applications of Microhardness Testing in Geology

 

  • Quantitative Mineral Hardness Characterization
    Unlike the traditional Mohs scale, which is qualitative, microhardness testing provides numerical values (e.g., Vickers Hardness Number) for mineral hardness. This allows for more accurate comparisons, the detection of subtle differences between visually similar minerals (e.g., calcite vs. aragonite), and even insights into compositional zoning within a single crystal (e.g., core-to-rim changes in garnet).
  • Ore Comminution Studies
    The hardness of individual mineral phases affects how rocks fracture and grind. Harder minerals may resist fragmentation, remaining as coarse particles and potentially trapping softer or valuable phases. Microhardness data supports modeling of ore fragmentation and optimization of grinding processes.
  • Coal Weathering and Oxidation Monitoring
    Research—including early studies by Given & Nandi in the 1970s—has shown that coal microhardness can increase as it oxidizes due to chemical bonding changes. This makes microhardness a useful proxy for assessing coal oxidation and weathering, which impacts its gas content, coke-making quality, and storage stability.
  • Meteorites and Planetary Materials
    Understanding the microhardness of extraterrestrial phases can offer insights into their abrasion resistance, behavior during atmospheric entry, or response to impact events—key considerations in planetary science.
  • Construction Materials (Concrete Aggregates)
    Microhardness testing is also used to evaluate the hardness contrast between aggregate particles and the cement matrix. This helps in predicting wear resistance and polishing behavior in applications like industrial flooring.

Qness 10 / 60 M

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Why our equipment?

  • High-precision indentation at micron scale
  • Automated measurements and imaging for efficient workflows
  • Compatibility with polished geological specimens
  • Absolute hardness values in MPa or kgf/mm², allowing detailed material comparisons

Even fine distinctions—such as different hardness values in polymorphs or across compositional zones—can be captured with QATM instruments, supporting both research and industrial applications.

Grain Size Analysis of Sediments and Soils with Laser Diffraction

This application is used for sedimentology studies (e.g., analyzing river, marine, or aeolian sediments), soil science and environmental geology (e.g., understanding contaminants depends on sediment grain sizes).

Grain size distribution reveals information about the depositional environment and material properties in fact can help in interpretating energy conditions of deposition. It is also used in stratigraphy and paleoclimate studies as particle size can indicate wind strength in past climate. In geotechnical engineering soil particle size affects permeability, compaction, and strength. Furthermore regulatory frameworks sometimes require soil particle size analysis for land reclamation or erosion risk assessment.

Traditionally, sieve methods as provided by Retsch are also used, but laser diffraction offers a much faster and detailed measurement across the full range. This has led to many labs adopting laser particle sizers for routine analysis of sediment cores, soil. 

Laser diffraction from Microtrac offers fast, high-resolution particle size analysis with minimal sample needs. It detects fine particles better than sieves/pipettes and follows ISO 13320 and ASTM B822 standards for accuracy. Studies show good agreement with traditional methods when dispersion is adequate. Its automation, reproducibility, and ability to analyze small or rare samples make it ideal for modern sedimentology and geology labs and geological agencies (like USGS - United States Geological Survey). 

Gas Storage Capacity of Coal and Shale (Methane/CO₂ Adsorption Isotherms)

High-pressure gas adsorption isotherm measurements on coal or shale samples to determine how much gas (methane or carbon dioxide, typically) these rocks can adsorb. This application underpins assessments of coalbed methane (CBM) resources, shale gas capacity, and the viability of CO₂ sequestration in coal seams or shale formations (often coupled with Enhanced Gas Recovery concepts).

Understanding how gases interact with coal and shale is critical for energy exploration and carbon management. High-pressure adsorption studies reveal how much gas can be stored, recovered, or sequestered under real reservoir conditions.

Key Applications:

  • Coal mining & CBM exploration: Methane adsorption capacity (Langmuir volume) indicates how much gas a coal seam can hold.
  • Shale gas evaluation: Measuring both methane and CO₂ adsorption provides insight into gas-in-place and preferential sorption (CO₂ often binds more strongly, enabling enhanced methane recovery through CO₂ injection).
  • Carbon sequestration: Adsorption studies determine how much CO₂ can be securely stored in unmineable coal seams or organic-rich shales, with focus on stability and kinetics.

Microtrac’s BELSORP high-pressure systems deliver precise adsorption isotherms up to several MPa, replicating reservoir conditions (0–5 MPa for methane). These instruments support international standards (ISO 18866 in development, ISO 15901-2:2022) and national norms such as China’s GB/T for coal methane sorption. By quantifying parameters like Langmuir volume and pressure, the technique underpins reserve estimation, CO₂-enhanced coalbed methane recovery, and greenhouse gas sequestration strategies. With standard, reliable data, geoscientists can design and optimize reservoir operations—making high-pressure adsorption analysis fundamental for both energy resource development and environmental management.  

Wollastonite Morphology Analysis

Wollastonite (CaSiO₃) is a naturally occurring chain silicate that crystallizes in acicular (needle-like) forms. Its aspect ratio (length/width) and particle shape distribution critically determine its reinforcing effect in plastics, paints, friction products, and ceramics. Conventional size analysis by sieving or diffraction provides only equivalent spherical diameters and fails to characterize elongated morphologies. Dynamic Image Analysis (DIA) with the Microtrac CAMSIZER M1 enables a quantitative and reproducible assessment of both particle length and thickness, delivering a complete morphology profile.

Why is important to choose DIA analysis?

  • Simultaneous measurement of particle size and shape parameters (length, width, aspect ratio, sphericity).
  • High statistical significance: thousands of particles measured per second for reproducible, representative data.
  • True acicular particle characterization: differentiation of elongated vs. equant grains, impossible with diffraction alone.
  • Non-destructive analysis with real particle images available for verification and documentation.
  • Applicable across mineral processing workflows, from comminution control to quality control of final mineral products.

Particle Morphology Characterization:

DIA simultaneously records thousands of high-resolution images per second, providing length and width distributions, aspect ratio, elongation, and sphericity. For acicular minerals like wollastonite, these parameters are essential for correlating morphology with functional properties.

Standard Methods:

  • ISO 13322-2: Particle size analysis — Image analysis methods
  • ISO 13320: Laser diffraction methods (complementary for size distribution)

Enabling Progress in GEOLOGY AND MINING

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