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January-February 2018

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Hematite Twins from the Kalahari Manganese Field, Northern Cape Province, South Africa

If they are well known and easily recognized, twinned crystals arouse the interest of many mineralogists and mineral collectors. Twins of calcite, especially from specific localities such as Egremont, Cumbria, England, iron-cross twins of pyrite, and cyclic twins of aragonite and rutile are good examples. Here we report on twins of hematite from the Kalahari manganese field in South Africa, which are beautiful and rare examples of twinning. These have largely been overlooked and have not been previously described in detail. The minerals of the Kalahari manganese field formed from the hydrothermal alteration of Precambrian sedimentary manganese ore beds and hematitic banded iron formations. Excellent discussions of this region and the minerals found there are provided by Cairncross and Dixon (1995), Cairncross, Beukes, and Gutzmer (1997), and Cairncross and Beukes (2013).


Dr. R. Peter Richards is a consulting editor of Rocks & Minerals and an avid mineral collector with special interests in crystal morphology, twinning, and epitaxy.

Dr. Mirjan Žorž is a passionate mineral collector who specializes in crystal morphology of elongated, twisted, and twinned minerals with a special emphasis on their symmetry properties.

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