1. Dept. of Mining Engineering, Univ. of South Africa, Florida Campus Private Bag X6, Johannesburg 1710, South Africa (corresponding author). ORCID: .
2. Professor, Dept. of Geology and Mining, Univ. of Limpopo, Private Bag X1106, Sovenga 0727, South Africa. ORCID: .
3. Professor, Dept. of Mining Engineering, Univ. of South Africa, Florida Campus Private Bag X6, Johannesburg 1710, South Africa. ORCID: .