Microstructure and Crystallographic Preferred Orientation (Cpo) of Hematite Ores From the Sishen Mine, Northern Cape Province, South Africa

Abstract

Banded iron fonnatiotis (BIFs) are described as banded chetiiical sedimentary rocks composed of major amounts of magnetite, hematite and quartz, with variable atnounts of iron bearing tiiinerals like carbonates (e.g. siderite, ankerite) and silicates (e.g. greenalite, gtTmerite). The BIFs are tratisforined to high grade iron ores by removal of quartz and transformation of almost all iron bearing minerals to hematite. On macroscopic and microscopic scale the high grade hetnatite ores generally reveal a more or less visible lamination caused by alternating layers of different grain sizes. In addition to the microstructt.ire (grain size, grain shape etc.), the crystallographic preferred orientation is a powerful tool to characterize rocks and ores. The overall crystallographic preferred orientation (CPO, texture) of volumes can be determined by neutron diffraction and the local texture on small areas of polished sections by electron backscattering diffraction (EBSD). The CPO of volumes of all hematite ore types (including a conglomerate pebble) of the Sishen Mine is characterized by a weak, usually circular c-axis maximum aligned to the normal of the lamination of the ores, and seems to be typical for this essentially unmetamorphosed and undeformed ores. The crystallographic otietitation of grains of the hematite ores determined locally by EBSD shows in general the same preferred orientation. But, it is remarkable that partially the CPO is quite different and inherited from grain orientations of preceding primary minerals (e.g. magnetite, goethite, siderite/calcite, ankedte/dolomite) of the Banded Iron Formation, without any microscopic visible indication.

Experimental Research on the Determination of the Coefficient of Sliding Wear under Iron Ore Handling Conditions

“…For the stationary particle, the average temperature rise ∆Tp is estimated by [28], 0.5 p T NL  (11) where N is estimated temperature irrelative of sliding speed, and L is a dimensionless parameter. N and L are respectively given by equations (12) and (13) [28,29],…”

“…Siemes [11] investigated the microstructure and texture. However, the hardness of Sishen iron ore particles has not yet reported.…”