Editing Tsumeb (section)

=== Minerals ===
Tsumeb is notable for the huge mineralized pipe that led to its foundation. The origin of the pipe has been hotly debated. The pipe penetrates more or less vertically through the Precambrian Otavi dolomite for at least 1,300 m. One possibility is that the pipe was actually a gigantic ancient cave system and that the rock filling it is sand that seeped in from above. If the pipe is volcanic, as some have suggested, then the rock filling it (the "pseudo-aplite") is peculiar in the extreme. The pipe was mined in prehistoric times but those ancient workers barely scratched the surface. Most of the ore was removed in the 20th century by cut-and-fill methods. The ore was [[polymetallic]] and from it [[copper]], [[lead]], [[silver]], [[gold]], [[arsenic]] and [[germanium]] were won. There was also a fair amount of [[zinc]] present but the recovery of this metal was always difficult for technical reasons. Many millions of tonnes of ore of spectacular grade were removed. A good percentage of the ore (called "direct smelting ore") was so rich that it was sent straight to the smelter situated near the town without having to be processed through the mineral enrichment plant. The Tsumeb mine is also renowned amongst [[mineral collector]]s. Tsumeb belongs to the world's most prolific mineralogical sites. The minerals from Tsumeb are unsurpassed in variety and quality of form.<ref>{{cite web|title=Mineralienatlas – Fossilienatlas|url=https://www.mineralienatlas.de/?l=969&lang=de|website=www.mineralienatlas.de|language=de|access-date=2020-05-10}}</ref>

At least 170 mineral species have been cataloged and 20 of these are found nowhere else.  The concentration of ingredients for Tsumeb's mineral formations originates in a sulfide deposit rich in many metals. A non-arid environment plentiful in oxygen-rich groundwater contributed to leaching and re-deposition of these elements as new minerals, sometimes in crystalline formations.  There are rare [[Supergene (geology)|secondary minerals]] of Pb, Cu, Zn, As, Sb and, reflecting the ore deposit chemistry, Ge, Ga and Cd as well. Minerals first described from Tsumeb include, according to [[Mindat.org]]:
* rare (but also a few common) [[arsenates]]: andyrobertsite, arsenbrackebuschite, arsendescloizite, arsentsumebite, [[biehlite]], calcioandyrobertsite, chudobaite, [[duftite]], ekatite, fahleite, feinglosite, ferrilotharmeyerite, gaitite, gebhardite, gerdtremmelite, helmutwinklerite, jamesite, johillerite, keyite, koritnigite, leiteite, ludlockite, lukrahnite, molybdofornacite, o'danielite, prosperite, [[reinerite]], schneiderhöhnite, schultenite, sewardite, stranskiite, thometzekite, tsumcorite, [[warikahnite]], wilhelmkleinite, zincgartrellite and zincroselite
* unique [[germanium]] (bartelkeite, calvertite, eyselite, fleischerite, [[germanite]], itoite, [[krieselite]] (germanate topaz), mathewrogersite, otjisumeite, ovamboite, schaurteite and stottite) and [[gallium]] (gallobeudantite, söhngeite, tsumgallite) minerals
* others are: kegelite, minrecordite, otavite, plumbotsumite, queitite, sidpietersite (unique [[thiosulphate]]), stibioclaudetite, [[tsumebite]] and zincrosasite.<ref>{{cite web|url=http://www.mindat.org/loc-2428.html|title=Tsumeb Mine (Tsumcorp Mine), Tsumeb, Oshikoto Region (Otjikoto Region), Namibia|website=www.mindat.org|access-date=18 April 2018}}</ref><ref>{{cite web|url=http://www.handbookofmineralogy.com|title=Handbook of Mineralogy|website=www.handbookofmineralogy.com|access-date=18 April 2018}}</ref><ref>{{cite web|url=http://www.webmineral.com|title=Mineralogy Database|website=www.webmineral.com|access-date=18 April 2018}}</ref>

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<gallery caption="Minerals of Tsumeb" widths="200px" heights="200px" perrow="5">
File:Azurite-den07-03d.jpg|Very large cluster of [[azurite]] crystals, ex-[[Smithsonian]] collection, offered at US$125,000. Size 16.7 x 13.2 x 10.5&nbsp;cm.
File:Calcite-Hematite-163162.jpg|[[Calcite]] crystals colored red by tiny inclusions of [[hematite]]. Size: 9 x 9 x 4.3&nbsp;cm.
File:Cerussite-173904.jpg|Zoned [[Cerussite]] crystal, 5.9 x 3.6 x 1&nbsp;cm.
File:Dioptase-39887.jpg|Gem-quality [[dioptase]] crystals. Tsumeb mine is the source of many of the world's best (and most expensive) dioptase specimens.
File:Dioptase-denv08-28b.jpg|[[Dioptase]] crystals on calcite, a classic Tsumeb specimen. Size: 8.2 x 5.8 x 5.5&nbsp;cm
File:Leiteite-rare08-2-77b.jpg|Leiteite, a zinc [[arsenate]], colored umber-red by inclusions of Ludlockite, a lead arsenate. Tsumeb is the [[type locality (geology)|type locality]] for both species. Size: 2.8 x 1.8 x 1.2&nbsp;cm.
File:Malachite-Azurite-173869.jpg|[[Malachite]] [[pseudomorph]]s after [[azurite]], 13 x 6 x 4&nbsp;cm.
File:Mimetite-Wulfenite-18689.jpg|Gemmy [[mimetite]] with a "sidecar" of [[wulfenite]], 2 x 1 x 1&nbsp;cm.
File:Scorodite-18800.jpg|Bright blue [[scorodite]] crystals on brown-black beudantite, 8 x 5 x 3&nbsp;cm.
</gallery>

In respect of it being 'one of the richest ore deposits with respect to variety, rarity and aesthetics of minerals in the world', the [[International Union of Geological Sciences]] (IUGS) included the 'Tsumeb Ore Deposit' in its assemblage of 100 'geological heritage sites' around the world in a listing published in October 2022. The organisation defines an IUGS Geological Heritage Site as 'a key place with geological elements and/or processes of international scientific relevance, used as a reference, and/or with a substantial contribution to the development of geological sciences through history.'<ref>{{cite web |title=The First 100 IUGS Geological Heritage Sites |url=https://iugs-geoheritage.org/videos-pdfs/iugs_first_100_book_v2.pdf |website=IUGS International Commission on Geoheritage |publisher=IUGS |access-date=13 November 2022}}</ref>