New Tsumeb Update 05 October 2021

4 October 2021

THIS week we return to Tsumeb for both our updates with many thumbnail and miniature specimens plus a smattering of small cabinet display pieces.

As mining progressed ever deeper at Tsumeb, the variety of metals in commercial quantity grew and looking back it is now classified as a copper, lead, zinc, silver, arsenic and germanium producer. Gold is often also quoted as a commercial product but as to just how much was produced, I do not know. Any gold must have been finely disseminated throughout the ore, certainly not visible in specimen form from my knowledge.

Over 91 years of production, between 1905 and 1996, about 30 million tons of ore was removed, yielding 2.8 million tons of lead, 1.7 million tons of copper and at the lower end of the scale, 80 tons of germanium. During the earlier days of mining there was probably very little demand for metals such as germanium and gallium but, as semi-conductors, these became increasingly important metals with the growth of the electronics and computing industries.

As lead was top of the production list, let’s begin with Galena. Despite lead being the most plentiful of all the metals at Tsumeb, well crystallised Galena is remarkably scarce. Hence this superbly crystallised miniature will make an excellent addition to any collection. Three cubic Galena crystals form an inter-grown cluster with the largest measuring 2.5 cm on its longest edge. These are partly overgrown by greyish-cream Dolomite crystals with scattered gemmy crystals of yellow Mimetite up to 9 mm long. For Tsumeb, it is a really good miniature Galena.

While on the subject of ore, such specimens seldom feature in Tsumeb collections, simply because run-of-mill ore was hardly ever collected, hence we tend to get a highly distorted snapshot of the orebody itself, with the emphasis entirely focused on well-crystallised specimens. Just occasionally such a specimen has been preserved and today we have a great example of a complex mixture of Renierite with Germanite, Bornite, Chalcopyrite, Tennantite and Pyrite. All six species can be readily identified by eye in this small cabinet specimen, with one label indicating it was mined in 1962.

Other rare minerals in this update include Alamosite and Schultenite. Alamosite is a rare lead inosilicate which forms sprays and platy colourless to white crystals at Tsumeb. This example is a 0.5 x 0.5 x 0.2 cm part crystal, kept secure and displayed in a small flat Perky box with a hinged lid and clasp. The specimen of Schultenite occurs with Zincolivenite as glassy, colourless to white cleavages measuring to 1.1 cm. Schultenite is a lead arsenate. The Zincolivenite forms mint and emerald-green blades and patches in a metallic grey Tennantite matrix. We also have another Zincolivenite miniature with even larger well-developed crystals, so take a look at this also, although this does not contain any Schultenite.

Of the various varieties of Aragonite found at Tsumeb, rich in lead, zinc and copper, the Cuprian variety is probably the least common. This large miniature of copper-rich Aragonite has a 9 mm thick crust of banded pale sky blue to turquoise-blue Aragonite covering a dense grey Dolomite matrix. The Aragonite’s surfaces form as rippled waves overprinted by bubbly botryoidal Aragonite spherules of about 1 mm diameter. It is a lovely specimen and a little bit different for a Tsumeb collection.

Today we feature some delightful thumbnail specimens amongst which are two Azurites, a Cuprite, two very different Wulfenites and a gorgeous Tennantite. Tennantite is not always the most aesthetic of minerals, but this one certainly is! Three steely blue-grey, razor-sharp tetragonal crystals of Tennantite sit on a tiny matrix of micro-crystalline brassy-golden Pyrite. One Tennantite crystal dominates, measuring 2.2 cm tall with the two much smaller crystals interpenetrating at its base. The crystals have a metallic lustre, displaying subtle shades of steely-blue.

One of today’s larger specimens is a Mimetite with Wulfenite. Excellent creamy lemon lustrous sprays of Mimetite crystals are clustered over a 5 x 4 cm area of matrix, some with a vivid apricot-orange iron-oxide tint on the terminations. In addition, tabular crystals of dark chocolate brown Wulfenite perch on the red-dark chocolate brown Hematite-Goethite matrix, making a very distinctive small cabinet specimen.

Let’s end our review with a lovely and rare example of Malachite pseudomorphing after Cuprite. Despite Malachite and Cuprite being almost ubiquitous throughout the mine, such pseudomorphs are rarely seen and especially to this degree of sharpness. Both Cuprite crystals measure 3 to 4 mm across and are perched opposite one another at one end of a crystallised Calcite matrix. This is a rare and perfectly formed example from Tsumeb.

Take some time to look through all 21 specimens if you can because there are many others not mentioned which might just fit the bill! No matter how common a mineral may be at Tsumeb, it usually offers some habit, colour, shade or association which is new and worthy of more investigation. That’s why it’s a collector’s delight! Enjoy today’s selection and, like The Terminator, we’ll be back on Friday with more! 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.

 

DATES FOR YOUR DIARY

Crystal Classics, and our sister company UK Mining Ventures, will be in attendance at the following shows for the remainder of 2021:

OCTOBER 22-24
The Munich Show 2021
Exhibition Center Messe München, WEST Entrance, Munich, Germany

NOVEMBER 20
The Sussex Mineral & Fossil Show 2021
Haywards Heath College, Harlands Road, Haywards Heath, West Sussex RH16 1LT, UK

NOVEMBER 27
Crystal Classics Winter Open Day 2021
No.1, The Old Coach Yard, East Coker, Somerset BA22 9HY, UK

 

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MINERAL WISH LIST

We also offer an additional service that enables you, as our customer, to contact us via orders@crystalclassics.co.uk with your mineral wish list to enhance your current collection, but are unable to find the right specimens on our website. We have 1000's of specimens in our general stock that do not appear online.

Author: JH
Categories: Updates

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