e-journal of mining engineering is a peer-reviewed, open access journal published by Petroleum Journals Online. It is concerned with the theory and practice of finding, extracting, and preparing coal, metals, and minerals. We do not charge readers any access fees. Papers are published within 2 to 3 months of initial submission. This journal participates in LOCKSS and CLOCKSS archival systems. Authors retain their copyright. Articles are covered by Creative Commons CC BY-NC-ND 4.0 license terms.