• Ash Fusibility Testing >
• Grindability testing in mining: bond work index determination >
• Iron Ore Reducibility Test >
• Monitoring Particle Size in Mineral Processing >
• Optimizing Mining Processes with Laser Diffraction and Image Analysis >

• Nitrogen Physisorption for Surface Area and Microporosity Analysis of Geological Materials >
• Microhardness Testing of Minerals and Rocks >
• Mercury Porosimetry for Rock Porosity and Pore Size Distribution >
• Pilot Plant Furnaces for Coal and Coke Testing >

GRINDABILITY TESTING IN MINING: BOND WORK INDEX DETERMINATION WITH RETSCH

Accurate Ore Hardness Measurement for Smarter Circuit Design

In the mining and minerals industry, understanding how hard an ore is to grind is essential for designing energy-efficient and cost-effective comminution circuits. The Bond Work Index (BWI) test is the globally recognized method for determining the energy required to grind an ore to a specific particle size. Whether you are designing a new processing plant or optimizing an existing one, knowing the grindability of your material is a critical first step.

Retsch offers an efficient and user-friendly solution for Bond testing with its Drum Mill TM 300 which can be used as Bond Index Tester. This machine is adapted to meet the specific requirements of this standardized procedure.

Why Perform Bond Work Index Testing?

There is also another example about SYNC and the combination of laser diffraction and dynamic image analysis, to improve energy efficiency and reduce carbon footprint in magnetite and iron ore beneficiation. The key goal is optimizing particle size and magnetic conditioning to enhance downstream processes like flotation. By analyzing particle size and shape from the same sample, the system avoids sampling errors and ensures accurate data.

Read the application note: Magnetite and Iron Ores: Potential Use of Diffraction Particle Size Distributions in Combination with Simultaneous Image Analysis to Achieve Higher Energy Efficiency and Smaller Carbon Footprint

Nitrogen Physisorption for Surface Area and Microporosity Analysis of Geological Materials

Nitrogen gas adsorption at cryogenic temperatures (77 K) remains a cornerstone technique in geoscience and materials research for determining the specific surface area and microporosity of minerals, ores, and derived materials. Using the Microtrac BELSORP series, researchers and laboratories can gain detailed insight into nanoscale porosity and surface characteristics—crucial for interpreting mineral behavior, adsorption capacity, and processing efficiency.

This method is widely applied across various geological materials such as clays, zeolites, activated carbons, bauxites, shales, and iron ore sinters. It is equally relevant in cutting-edge fields like planetary geology, where mineral porosity offers clues to the formation and alteration of extraterrestrial bodies.

Standards Methods

Microtrac systems support data evaluation according to international guidelines, ensuring accuracy, reproducibility, and comparability:

• ISO 9277:2010/2022 – Defines BET surface area measurements and validation criteria (linearity, C constant, etc.)
• ISO 15901-2:2022 – Covers mesopore analysis and pore size distribution via methods such as NLDFT
• ASTM D3663 – Standard practice for BET surface area analysis of catalysts, showing cross-industry relevance

Nitrogen physisorption using Microtrac analyzers delivers critical insights into surface area and porosity that cannot be obtained through bulk chemistry or microscopy alone. Whether studying mineral adsorptive capacity, coal rank, or extraterrestrial material, BET analysis offers a standardized, precise view into the nano-scale structure of geological samples—backed by the quality and reliability of Microtrac technology.

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 and Geometallurgy

 The hardness of individual mineral phases strongly influences ore breakage and grinding behavior. Harder minerals may resist fragmentation, remaining as coarse particles and potentially entrapping softer or valuable phases. Microhardness data supports mineral liberation studies and helps optimize comminution models, directly contributing to process efficiency.

Coal and Shale Mechanics

 Microhardness testing is increasingly applied to coal and shale to evaluate their mechanical properties in relation to unconventional gas reservoirs. Measurements provide insights into brittleness, strength, and fracturing behavior, supporting methane recovery and shale gas development.

Planetary and Extraterrestrial Materials 

Understanding the microhardness of minerals in meteorites and lunar samples helps assess their abrasion resistance, response to impact events, and susceptibility to space weathering. These studies contribute valuable information to planetary exploration and the interpretation of extraterrestrial material behavior.

Mercury Porosimetry for Rock Porosity and Pore Size Distribution

Mercury Intrusion Porosimetry (MIP) is used to characterize the pore volume and pore size distribution of rocks, ores, and other solid materials by forcing mercury into the pores under pressure.

Porosity is a key property: it’s the storage capacity for fluids in rocks and the determinant of how fluids move (permeability is related to pore throat sizes). While overall porosity can be measured by simpler means (like saturation or helium pycnometry), MIP uniquely provides a pore size distribution (PSD) over a wide range. This is valuable for Reservoir quality evaluation. Given porosity, a sample with predominantly large pores will generally have higher permeability than one where porosity is in micropores. Mercury intrusion gives an idea of effective pore throat sizes controlling flow. Rock typing: Two sandstones might both have 20% porosity, but if one has it mostly in 10 µm pores and the other in 0.1 µm pores, their behavior differs. MIP can differentiate such cases, helping geologists classify reservoir rock types.

In mining and mineral processing, knowledge of pore sizes can influence how one grinds or processes an ore. For example, if an ore’s valuable mineral is contained in matrix that has very small pores, leaching solution might not penetrate well – you’d need to crush finer or pretreat. MIP could quantify those pore entry sizes to inform such decisions.

To sum up, mercury intrusion porosimetry provides geologists and mining engineers with a window into the pore architecture of rocks and materials, quantifying total connected porosity and the size distribution of those connections from a few nanometers up to visible voids. This information is essential for predicting how fluids interact with the material – whether that be oil migrating through a sandstone, or acid leach solution percolating through crushed ore, or simply water entering a building stone and causing weathering.