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Paper Number: 542

Gemstones of Southern Africa: a tour of the subcontinent

Cairncross, B.

Department of Geology, University of Johannesburg, Johannesburg brucec@uj.ac.za

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Southern Africa, and South Africa and Botswana in particular, is best known for diamonds as the primary gemstone in the region. However, within the borders of Namibia, Zimbabwe, Zambia, South Africa and Mozambique, a host of other gemstones are found, many of which are exploited by informal artisanal miners. These include beryl (aquamarine, emerald, morganite and heliodor), chrysoberyl (alexandrite), gem-quality cordierite, corundum variety ruby corundum, garnet (demantoid, hydrogrossular, rhodolite and spessartine varieties), jeremejevite, quartz (agate, amethyst, carnelian, blue chalcedony, chrysoprase, citrine, rose quartz, tiger’s eye and pietersite), sugilite, topaz and tourmaline (elbaite and indicolite) [1].

This submission will highlight the location, geological setting and discuss examples of outstanding gemstones from southern Africa, for example, from Namibia: the Erongo Mountains in have produced the finest aquamarine and gem-quality jeremejevite in Southern Africa [2]; Goboboseb Mountains west of the Brandberg yield high quality amethyst [3]; The pegmatites of central Namibia produce gem quality elbaite and indicolite tourmaline; Klein Spitzkoppe topaz [4]; Spessartine garnet from Marienfluss. From South Africa [5]: Gravelotte emeralds from the GEM mine in the Murchison Mountains; Diamonds from kimberlites and alluvial deposits in the Northern Cape Province; Gem quality hydrogrossular garnet from the Bushveld Complex; Tiger’s eye and jasper from Griquastad in the Northern Cape Province. From Zimbabwe: Topaz from St Ann’s mine in Mwami; Chrysoberyl (alexandrite) from Novello claims, Masvingo [6]. From Mozambique [7]; Tourmaline from the Alto Ligonha pegmatite belt, and several varieties of gem quartz from various localities.

Figure 1: A selection of faceted coloured gemstones from Southern Africa.

References:

[1] Cairncross, B. (2001). First Field Guide to Gemstones of Southern Africa. Struik New Holland Publishers, Cape Town, 57 pages

[2] Cairncross B and Bahmann (2006). The Mineralogical Record (37): 361-470

[3] Cairncross B and Bahmann (2006). Rocks & Minerals (81): 442-457

[4] Cairncross et al (1998) Gems & Gemology (34): 114-125

[5] Cairncross B (2004) Field Guide to Rocks & Minerals of Southern Africa. Struik New Holland Publishers, Cape Town, 297 pages

[6] Schmetzer K et al (2011). The Australian Gemmologist (24): 133-147

[7] Bettencourt Dias M and Wilson WE (2000). The Mineralogical Record (31): 459-497