New Africa & South America Update 18 January 2022

18 January 2022

WE like to try out new themes in our weekly updates and last week decided on a joint Africa and South America selection for today, with reference to their once common origin while joined together prior to the Jurassic. The connecting theme is that of continental drift and the ongoing processes of accretion and subduction along plate boundaries.

Between making our selection of specimens and them going live today, we witnessed last Saturday perhaps the biggest manifestation of tectonic processes in 30 years with the catastrophic eruption of Tonga's Hunga-Tonga-Hunga-Ha'apai volcano. Whereas the separation of South America from Africa is along the mid-Atlantic accretion zone, the Polynesian volcanos lie on the Kermadec-Tonga subduction zone, where the Pacific Plate descends beneath the Kermadec and Tonga Plates.

What are now the continents of South America and Africa were once part of Gondwana, a supercontinent which formed about 550 million years ago. The close similarity of ‘fit’ between their adjacent coastlines (especially their continental shelves) was one of the first triggers to the, then, theory of continental drift. Many of the specimens in today’s update would have formed in Gondwana, only beginning to part company when the initial breakup began about 180 million years ago. So let us begin our specimen review in South America, then head east to Africa.

We have two good examples of Cassiterite, both from Bolivia. One is a miniature group of jet-black crystals to 1.5 cm forming a miniature domed mass from Huanuni mine. The other is what appears to be a floater of Cassiterite with Sphalerite and Quartz from the Viloco mine in Loayza Province. One rather unusual specimen is a superb Ludlamite on Pyrite, again from the Huanuni mine, displaying two interlocking deep apple green Ludlamite crystals to 3 cm. These sit on a bed of micro-crystallised Siderite overlaying a block of golden massive Pyrite. Also from Bolivia is a nice cog-wheel Bournonite from Viboras mine in the Department of Potosí.

Our one offering from Peru is a superb Hübnerite with Quartz from Mundo Nuevo in Sanchez Carrion Province. This superb miniature is a sculptural mix of black metallic Hübnerite crystals and elegant, acicular colourless Quartz crystals, all emerging from a thin plate of Quartz and dominated by a magnificent 4.4 x 2.5 x 0.9 cm Hübnerite crystal.

Vivianite with Ludlamite provides a lovely combination of phosphate minerals from the Cabeça do Cachorro Claim in Amazonas State, Brazil. A cluster of metallic blue-green Vivianite crystals to 5 cm long sit flat against a sooty black, micro-botryoidal carpet of drusy Siderite. Scattered over this are three limey apple green Ludlamite crystals, each to about 7 mm long.

Last but certainly not least from South American are two superb Tourmalines from Brazil. One is a large gemmy Quartz crystal with three deep leaf green Uvite crystals attached, from Brumado in the State of Bahia and the other, a sublime Indicolite Elbaite from the Santa Rosa Mine in Minas Gerais. This 8.8 cm long crystal is from a Tourmaline-rich granite pegmatite within the Eastern Brazilian pegmatite province and is a gemmy, uniform rich deep indigo blue with a deep leaf green Mercedes-Benz trigonal termination.

Having crossed the South Atlantic Ocean, which widens at a rate of 3.8 cm (1.5 inches) per year, we have a fine selection of minerals to represent Africa. Beginning in Morocco, see the calcium-manganese arsenate Talmessite and a terrific Erythrite, both from the Bou Azzer mining district. A lovely Dioptase on Calcite and an aesthetic lemon-yellow Mimetite can only be from Tsumeb mine in Namibia!

A quite rare species is Fluor-liddicoatite from Estatoby in the Sahatany Valley of central Madagascar. Two superb translucent plum purple Fluor-liddicoatite crystals are intergrown on a small matrix of creamy white Albite Feldspar. This is a wonderful specimen.

Do have a look also at the Arfvedsonite with well crystallised Feldspar from Mount Malosa in Malawi; a charming Quartz Sceptre Amethyst from the Chiredzi mining district in Zimbabwe and a superb, museum size (and quality!) Malachite on Chrysocolla from the L'Etoile du Congo mine in the Katanga Copper Crescent of the Democratic Republic of the Congo (DRC).

Our final destination is South Africa. From the Kalahari Manganese Field in Northern Cape Province we have two excellent yet very different Rhodochrosites and a well-priced example of Manganvesuvianite from N'Chwaning II mine. Two rarer species are an Ephesite from the Postmasburg Manganese Field, also in Northern Cape Province and a Zirkelite with Phlogopite, Fluorapatite and Diopside from the famous Palabora mine at Loolekop in Limpopo Province.

We hope that between these two continents there is a selection you will enjoy browsing through and for more information on any individual specimen, simply use the hyperlinks. Continental drift is a fascinating process which provides a driving force for continual mineral formation and evolution. Although we greatly enjoy these aspects, we also think of all people in Polynesia who have to endure tectonics more violent manifestations and so wish them all safe and well. Good hunting amongst today’s 21 and let’s hope you spot a good addition for your collection. PT

                                         

If you'd like to see a video of any of the specimens listed above then please contact us at orders@crystalclassics.co.uk and we'll be happy to assist you. We endeavour to respond to all enquires within 24 hours during weekdays, however at the weekend it might take us a little longer to respond.

 

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Author: JH
Categories: Updates

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