Abstract Manganese oxide, silicate and carbonate ores are mostly mined as feedstock for steelmaking where Mn is largely added as ferroalloy, but they are also used for battery and to a lesser extent fertiliser and pigment production. The physical, mineralogical and textural properties of manganese ore minerals are known to influence their thermal properties and thus their high temperature behaviour during sintering or alloy production. Microhardness testing using the Vickers indenter is a potentially valuable characterisation technique to correlate the physical and optical properties of Mn ore minerals with their mineral chemistry and texture when used in conjunction with electron probe microanalysis (EPMA) and helium pycnometry. Microhardness values can also inform potential beneficiation pathways for lower grade Mn ores and/or assist in the prediction of lump: fines ratios during mine planning. This study provides the results of microhardness testing of Mn ore minerals from several different Mn ore types with variable mineralogy and texture. The data indicates that there is a clear link between mineral microhardness and micro- to nano-scale porosity and microcrystallinity, leading to potentially large variations in microhardness for some common Mn ore minerals. For example, cryptomelane with lower reflectivity, interpreted as having higher nano- to micro-porosity and/or differences in microcrystallinity, has significantly lower microhardness (mean 267 kg/mm2) than cryptomelane with higher qualitative reflectivity (mean 629 kg/mm2). EPMA conducted on mineral grains subjected to microhardness testing showed microhardness values did not vary systematically with changes in mineral chemistry but did vary with total element content as determined by EPMA. Low analytical totals were a de facto semi-quantitative measurement of mineral nano- to micro-porosity due to likely beam splitting/dispersion on more microporous samples identified during optical microscopy. Although there was no systematic link seen between microhardness and tetravalent Mn mineral element chemistry in this instance (e.g., K in cryptomelane), cryptomelane with lower reflectivity has lower Mn contents and higher contents of minor elements such as Fe, Al and Si.

中文翻译：

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锰矿矿物的显微硬度表征——对下游加工的影响

摘要 氧化锰、硅酸盐和碳酸盐矿石主要作为炼钢原料开采，其中锰主要作为铁合金添加，但它们也用于电池，少量用于肥料和颜料生产。众所周知，锰矿石矿物的物理、矿物学和结构特性会影响它们的热特性，从而影响它们在烧结或合金生产过程中的高温行为。使用维氏压头进行显微硬度测试是一种潜在有价值的表征技术，当与电子探针微量分析 (EPMA) 和氦比重测定法结合使用时，可将 Mn 矿石矿物的物理和光学特性与其矿物化学和质地相关联。显微硬度值还可以为低品位锰矿石的潜在选矿途径提供信息和/或帮助在矿山规划期间预测块矿：细粉比。本研究提供了来自具有不同矿物学和质地的几种不同锰矿石类型的锰矿石矿物的显微硬度测试结果。数据表明，矿物显微硬度与微米至纳米级孔隙度和微结晶度之间存在明显联系，导致一些常见锰矿石矿物的显微硬度可能存在较大差异。例如，具有较低反射率的锂锰矿，被解释为具有更高的纳米到微孔率和/或微结晶度的差异，其显微硬度（平均 267 kg/mm2）比具有较高定性反射率（平均 629 kg/mm2）的镍锰矿低。对经过显微硬度测试的矿物颗粒进行的 EPMA 表明，显微硬度值不会随着矿物化学的变化而系统地变化，但会随着由 EPMA 确定的总元素含量而变化。由于在光学显微镜中发现的更多微孔样品上可能存在光束分裂/色散，因此低分析总数实际上是矿物纳米到微孔率的半定量测量。尽管在这种情况下，在显微硬度和四价 Mn 矿物元素化学之间没有看到系统的联系（例如，钾锰矿中的钾），但具有较低反射率的钾锰矿具有较低的锰含量和较高的微量元素（如 Fe、Al 和 Si）含量。