SEM Image Comparison of Selected Crushed Mineral Standards Sample Preparation and Analysis

Abstract

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.