New South America Update 05 November 2021

4 November 2021

FROM Africa on Tuesday we cross the Atlantic and tour South America for today’s update. While Brazil largely dominates our selection, we also have fine minerals from Argentina, Bolivia, Chile and Peru.

In a past update on Africa we spoke of the ancient cratons which form the continent’s framework and so the same applies to South America. Greatly simplified, the continent has five major pre-1.6 Giga-year cratons, all dating from the first era of Earth history for which the geological record is more accurately preserved. Of these, by far the largest are those of Amazonia, São Francisco and Rio Apa. This update reflects mainly the economic minerals of South America, be these metallic ore minerals or gemstones, the latter for which Brazil is particularly associated, especially in the state of Minas Gerais. As on Tuesday, we will tour the countries in alphabetical order and so begin in Argentina.

The Capillitas mine in the Andalgalá Department of Argentina has produced specimens of Native Gold from the Nueva Esperanza vein and this rare cabinet specimen displays rich leafy bright metallic yellow plates scattered along the top surface of a rusty brown Limonitic Quartz matrix. The Native Gold forms bright hackly edged leaves highlighted with micro-triangular Native Gold crystals.

Bolivia is next on the agenda from where we have two excellent specimens, a fine crystallised Cassiterite and a stunning Vivianite. The Viloco mine is situated in the spectacular mountains of Loayza Province in western central Bolivia. From here, a cabinet specimen of beautifully developed translucent Cassiterite with crystals up to 1.8 cm in length and all with brilliant lustrous faces. The prismatic crystals are pale Champagne darkening almost to black. And from the tin-mining region around Llallagua, a spectacular, off-matrix specimen of beautifully crystallised Vivianite. Almost coal-black in reflected light, the Vivianite is a gorgeous deep electric lime-bottle-green in transmitted light. The crystals measure to 5 cm forming grouped clusters in parallel growth and all perfectly terminated. If this Vivianite is displayed backlit it will look stunning. What appear as almost opaque crystals in reflected light are revealed to be perfectly transparent to gemmy in transmitted light.

Now to Brazil with 13 specimens to offer, 12 of which are from the gem state of Minas Gerais. From here, and in no particular order, you can enjoy a red and green Elbaite Tourmaline from the Golconda Pegmatite; Phenakite from Rio Piracicaba; a gorgeous Spessartine Garnet with Quartz crystals from the Navegadora mine claim in Conselheiro Pena and two quite superb Aquamarine Beryl crystals from Barra de Salinas in Coronel Murta. These two similar Aquamarine prisms, being sold separately, have mirror-like lustrous faces and a colour more of pale blueberry milkshake than aquamarine! These are beautiful crystals of 10.4 and 11.7 cm tall.

Also from Minas Gerais, a lovely blocky prism of Columbite; Tantalite-(Mn) from Nazareno; Tapiolite from Baixão da Laje mine in Parelhas; Hematite from Casa de Pedra Mine in Congonhas do Campo and Ouro Preto in the Iron Quadrangle; Hydroxylherderite from Barra do Salinas; Brazilianite from the Córrego Frio mine in Linópolis and finally, Quartz from Diamantina in the Jequitinhonha Valley. Our one Brazilian offering not from Minas Gerais is a Rutile on Quartz from Serra das Éguas in Bahia. This terrific small cabinet specimen is a gorgeous combination of Rutile and Quartz in which bright metallic black Rutile crystals surround a vertical Quartz crystal, forming an almost complete necklace-like chain tilted at 45 degrees.

Next is Chile, from where we have a parallel-stacked cluster of hexagonal, steely-silver-grey Molybdenite crystals on a Talc-like matrix from Jardinera No. 1 mine at Inca de Oro and a rare example of the copper sulphate Kröhnkite from the Chuquicamata District. A rich vein of vivid sky blue Kröhnkite bisects the granular Quartz matrix where, across the display face, the Kröhnkite vein forms a boudinage (sausage-like) structure expanding from 1 cm to 4 cm thick.

Our final destination is Peru. From Casapalca in Huarochiri Province, a Sphalerite with Quartz and Chalcopyrite is packed with crystallographic interest. The Sphalerite forms multiple twinned crystals and embedded in these are many epitaxially aligned brassy gold Chalcopyrite crystals. Some areas grade to translucent golden Sphalerite as the iron content rapidly reduces, with some patches so golden, they almost become indistinguishable from the Chalcopyrite. Then from the Tamboras mine in Mundo Nuevo, a superb cabinet specimen of lustrous, lime green wedge-like crystals of Augelite measuring to over 1 cm, intergrown with abundant colourless prismatic Quartz crystals.

Noted above are some seldom encountered species, especially the Kröhnkite and Tapiolite. Tapiolite is the name given to chemically unanalysed members of the Tapiolite-(Fe) - Tapiolite-(Mn) series, both iron-manganese niobate-tantalates.

As with most South American minerals, even the more common species like Hematite look spectacular, so leave no stone unturned and investigate further. Every specimen in today’s update is worthy of more careful scrutiny on our website because all are aesthetic no matter how common or rare. Enjoy and we hope you find that special item to help fill a certain gap in your collection. PT

Here is what you have to look forward to in next week's update:

Tuesday 9nd November - Europe

Friday 12th November - Asia & Australasia

                                         

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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