The qualitative investigation observed, through scanning electron microscope (SEM)
analysis, the morphological (size and shape) characteristics that specimen-grade mineral
standards can exhibit on a microscopic scale following mechanical crushing. A hand-crushing
technique (via mortar and pestle) was used to represent the macroscopic mineral crushing that
occurs throughout the taconite mining industry. The results are intended to show how SEM
analyses of these crushed standards can be used as a point of reference for comparison to crushed
minerals found within the taconite ore and taconite mining by-products of Minnesota’s Mesabi
Iron Range. For this SEM-based investigation, standards were chosen as analogs to three
common minerals found on the western Mesabi Iron Range: quartz, magnetite, and
stilpnomelane. A fourth mineral standard (actinolite) was chosen as an amphibole mineral that
can occur in the contact-metamorphosed easternmost portion of the Mesabi Iron Range. The
findings show that mechanical crushing can generate elongated mineral particles (EMP) from all
four standards, including quartz. Simply put, an EMP is a particle having length-to-width ratio
≥3:1. Consequently, most – if not all – mineral processing and/or rock crushing operations
nationwide have the potential to generate elongated mineral particles.
Natural Resources Research Institute, University of Minnesota Duluth, 5013 Miller Trunk Highway, Duluth MN 55811-1442
SEM Image Comparison of Selected Crushed Mineral Standards Sample Preparation and Analysis.
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