A 30 kg nugget of Onganja copper is returning home to Namibia for posterity.

The Onganja mining district is situated in Namibia about 80 km NE of Windhoek, near the town of Seeis. Copper and molybdenite ores were mined there for many years, but for mineral collectors Onganja was particularly famous for its cuprite and malachite specimens.

In very early times local Ovambos travelled up to 500 km south from their homeland to mine copper in the Onganja area. They smelted the copper ores (chalcocite, cuprite and native copper) in the nearby Swakop and Tenne River valleys, where there was plenty of water and wood. Dr Andy Smith, a renowned archaeologist from UCT, collected pieces of slag and other artifacts in the Tenne valley during a mine visit in 1985. Archaeological evidence of stone buildings and furnace nozzles can also be seen in the Windhoek museum. European mining started at Onganja in the 19th century, when Namibia was then known as German South West Africa. From then on a succession of foreign and local mining companies owned and worked the Onganja mine; they included Otjizonjati, South West Africa Company, Emke, Rio Tinto Zinc, Navarro, Zapata, and Noranda. It was during Zapata’s time that the famous cuprite pockets were discovered in 1973, and their presence apparently side-tracked the miners who continued mining the oxide zone, which caused a large drop in copper yield. This was not the right type of ore needed for the flotation plant.

The Onganja cuprite crystals are particularly spectacular stones; large (up to 2 kg in weight and 14 cm in diameter), gemmy, red, perfect crystals, with many covered in a thin film of bright green malachite. Duncan Miller has facetted several cuprites from Onganja. On the Mohs’s scale cuprite is comparatively soft (3,5–4) so exceptional care must be taken that the stone doesn’t chip when it is being faceted and a wax lap is required for polishing.

Here is a photograph of one of the first cuprites Duncan faceted, probably in the mid-1980s, when the late Sigri Barrella gave him a batch to cut. One of the finished gems turned out to be 100 carats and Sigri was horrified that Duncan had quoted him R5/carat for the faceting. This particular stone weighs 27 ct. Onganja cuprites are said to be the best cuprite faceting material available.

There is a unique story behind this most unusual cuprite specimen seen below. A mineral collector called Rudy Wallenda, related to the famous circus trapeze artists family, was visiting a friend who was ill in bed. Rudy had just purchased the cuprite which his friend was holding in his hand. At that moment his friend died and the cuprite fell out of his hand onto the floor. When Rudy went to pick it up, he found that it had broken open and revealed the malachite crystals inside! 


To go back to the history of the mine; Noranda never actually mined Onganja, but sold it again in 1984 to John Gurney and Stuart Moir. Their intention was to work the cuprite pockets further, but by that time the mine had become flooded and despite many attempts at pumping out the water, they never reached the cuprite area. It is known that over the years many legal and illegal attempts were made to scuba dive into the flooded tunnels in search of the cuprite. The late Trish Immelman once recounted a story (Mineral Chatter October 2008) of when she and her husband Ted, the Conradies, the Skakels, and the late Father Tony Garman visited the mine in the late 1970s: 

“Father Tony was determined to be successful and so had added his Lilo, hard hat, torch and swimming costume to his kit. While the rest of the party waited anxiously at the entrance to the pitch-dark adit, which was big enough to drive a car into, Father Tony donned his gear and intrepidly set off into the watery darkness disturbing the bats and other inhabitants en route. Despite paddling around staring with his torch into the water, he found very little, as apparently scuba divers had been there long before him.“ (Below is a photo taken by Ludi von Bezing of the entrance to the adit of the Onganja mine.)

In 1987 John Gurney and Stuart Moir developed a method of acid leaching the Onganja dumps of oxide ore. This operation continued under the supervision of Stuart until 1995 when there was no more ore left in the dumps. However, one year prior to the start of the acid leaching, the local Tenne River had come down in a massive flood and severely eroded the river bed. The caretaker of the mine at that time discovered that two enormous pieces of native copper had been exposed, as well as other smaller nuggets. The large ones apparently each weighed approximately 250 kg and 400 kg. With the aid of a front-end loader they were put on a truck and sent to Windhoek to be sold as specimens, along with some other large nuggets, as Stuart felt they were too special just to be sent to a smelter. However, because of their overall size and weight, and the fact that the majority of mineral specimen buyers came from overseas, seemingly none of the dealers would buy the giant native copper specimens, so back they went to the Onganja mine.

There they all sat until 1995 when the very last of the 'cementation' concentrate was on its way to the Tsumeb smelter and Stuart Moir decided to have the giant chunks put on the truck as well, so that their copper value could be realised. There always was an unconfirmed report that the larger of the two pieces was rescued and made its way to the Tsumeb museum. However, from recent enquires with the assistance of Ernst Schnaitmann in Windhoek, Anneliese Bruns, the Curator of the Tsumeb Museum, has told us that despite working there for nine years, she has never come across these missing nuggets.

The large native copper ore specimen in the museum of the Rand Afrikaans University also comes from Onganja. This one belonged to the well-known Johannesburg mineral dealer Clive Queit, and was bought by the museum after Bruce Cairncross and Karl Messner accidentally discovered it in Clive’s garage in 1992. Ellen de Kock, the Scientific Officer at the Council for Geoscience in Pretoria, kindly sent us these two photographs below of the specimen:

And now we get to the final and main point of our story.................  another 30 kg chunk of Onganja ore has surfaced. 

Early last year (2015) the family of the late Horst Windisch contacted Malcolm Jackson, in his capacity as the vice-chairman of FOSAGAMS, about a 30 kg Onganja copper mineral specimen that had been in their collection since the late 1970s. They wished possibly to donate it to FOSAGAMS (the Federation of South African Gem & Mineral Societies). After chatting to them for a while about the specimen, Malcolm suggested that it might be better suited to go to the geological museum at the Department of Mines & Minerals at Windhoek in Namibia. He proposed this option because many Namibians with an interest in minerals tend to consider that the mineral collectors of the world just go to Namibia to “plunder and profit” from its heritage. Malcolm is also aware that some miners see mineral hunters as a nuisance, rather than as dedicated collectors with a scientific interest in their specimens. By giving this special piece of Onganja history back to Namibia, FOSAGAMS and the Windisch family hope to try to change this perception somewhat. They refer to some words that appeared in a Mineralogical Record of many years back in a story related to Tsumeb.

This donation is “dedicated to all the miners, living or dead, who have ever stopped to save a specimen”.

With the agreement of the Windisch family, Malcolm arranged for Graham Harrison to have the nugget delivered to Cape Town from Pretoria last October, and then Malcolm himself mounted it on a specially designed display stand. This explains the photograph on the first page of this article. Once the specimen was in Cape Town, Malcolm contacted Robert Carr (the current owner of Onganja), as well as the Namibian Department of Mines & Minerals and advised them that he would be bringing the donated specimen to the museum in January of this year.

The only request of the Windisch family is that there is some mention alongside the specimen that it has been donated by them. The late Horst Windisch was an avid collector of minerals, and his family originated from Namibia. They hope that this specimen will add in some part to the history of the Onganja mine.

Gerhard Windisch himself tells us the story about how Horst obtained this specimen:
“We were on a family holiday over December 1975 to January 1976, in what was then South West Africa (Namibia). While we were staying in Windhoek, one Sunday afternoon my dad decided to go to the Onganja Copper Mine to look for some minerals to add to his collection. Soon after we arrived at the abandoned mine, we found three big specimens of native copper.
My dad decided to take just one of the big native copper pieces. It took two schoolboys as well as my father to pick up the specimen and load it into our Volkswagen Kombi (Model T2) - in the back, on top of the engine. Once home, it took a further three people to carry the specimen from the car down into his study in Groenkloof, where it was displayed all the time until my parents moved out of the house in April 2009. My dad also had another smaller piece of native copper, which I have added to the small display of my dad’s hobby of mineral collecting in the Museum at Bonnievale. (Why Bonnievale you may ask? My cousin is the owner of the Bonnievale Museum, where there is also a collection of my grandfather’s paintings from my mother’s side. His name was Karl Franz Rösemann)”.

In early December 2015 Stuart Moir visited our club to see the Windisch specimen before it went home to Namibia. A couple of other large nuggets and some mineral specimens from Onganja were also brought in by members that day and we show photos of them below.  

Stuart positively identified them all as likely to have come from Onganja, and explained more about their mineral content. Stuart was sorry to hear that his giant 400 kg nuggets were not at Tsumeb museum and fears they probably did land in the smelter despite stories to the contrary. They were almost pure native copper and cylindrical in shape, and decidedly larger than the ones we had to show him. Also they were river tumbled and most of the associated minerals had been scuffed off. In his short visit with us Stuart had many stories to tell about his time on the mine, including the fact that he was the person who realised that most of the “malachite” ore was in fact brochantite, which dictated that the method of extraction be changed from floatation to a leaching process. We do hope that we shall be able to persuade him to return to our club soon to tell us more informative anecdotes of his time spent on the mine. Below are some of the Onganja mineral specimens that “partied” on the day of Stuart’s visit. (They are not to scale with one another, but all are small cabinet specimens). 



          The right hand specimen here is the 30 kg nugget that has been returned to Namibia.

Article by: Malcolm Jackson and Jo Wicht. December 2015
Photographs by: Jo Wicht, L Barrella, and E de Kock

The Onganja Mining District, Namibia. (B. Cairncross & S. Moir) Mineralogical Record, Vol 27, March–April, 1996.
Namibia: Minerals & Localities (1st edition). L von Bezing, R Bode, & S Jahn.
GemologyOnline Forum: the article written originally by Duncan Miller on faceting cuprite.

Our grateful thanks go to everyone who has helped in some way with the compilation of this story. 

January 2016