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Polished section of rhodochrosite from Capillitas

Photo Source : Jeff Scovil

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Rhodochrosite - Rhodochrosit - Rhodochrosite - Rhodochrosita

South America, Argentina : World largest rhodochrosite stalactites in the Capillitas Mine

Coordinates : 2734'S , 6618'W : Capillitas mine : Andalgalá, Catamarca, Argentina

The polymetallic sulphide veins of the Capillitas Mine in northeastern Argentina have been mined since the times of the Incas. Later mining activity continued under the Spaniards, the English and even the Germans. All to all more than 30 kilometer of adits were driven into the mountains, which makes Capillitas the largest mine in Argentina. It is also the one with the most diversified mineralogy and about hundred minerals are known from this locality, including world rarities like germanite, hessite, colusite and putzite.

Principal orebodies of the Capillitas mine are the Capillitas, Carmelitas, La Rosario, Ortiz, Restauradora, and 25 de Mayo veins. The sulphide mineralisation is clearly hydrothermal in origin and of tertiary age, i.e. the whole deposit as such is only a few millions years old. The mine is located quite high at 3000 - 3300 m altitude, so regular mining is a difficult venture here. Consequently sulphide extraction proved uneconomic at some stage and was abandoned decades ago.

There is however one specific geological curiosity, which makes Capillitas very special and well known even nowadays. Generally the gangue accompanying any sulphide vein consists out of quartz and calcite with minor amounts of baryte, dolomite, fluorite and some other minerals. In Capillitas rhodochrosite = manganese carbonate is the predominant, if not exclusive gangue mineral. In fact, most of the Capillitas vein consists almost entirely out of rhodochrosite with only minor amounts of sulphide minerals.

The rhodochrosite shows all sorts of banding and all shades of colours from almost white to rich pink to a yellowish brown. Often the bandings shows a distinct chocolate brown colour, which is called capilliite and is a very zinc rich variety of rhodochrosite. The most impressive and highly esteemed colour however is a deep crimson red, equalling the colour of the very best rhodochrosite specimen from world renowned localities such as the Home Sweet Home mine / Colorado or the Northern Kalahari Manganese Fields in South Africa. Unfortunately this very best colour is almost always hidden in the middle of stalactites and stalagmites and exhibits its outstanding beauty only when cut and polished.

The individual crystal size of the Capillitas rhodochrosite is generally small and only seldom reaches 1 cm, though the crystals easily aggregate to large masses and spectacular stalactites. In 1986 a large cavity was discovered within one of the veins with individual stalactites up to 0,5 m thick and 5 m long. Unfortunately only little documentation work was done on this cave with the photo shown above believed to be the only one in existence. This cave was plundered very rapidly and the stalactites were cut and polished and sold worldwide, founding the fame of the Capillitas rhodochrosite. Mining for rhodochrosite continues into the present and about 100 - 200 tons of ornamental rhodochrosite are produced annually in these days. Possibly there is another great cave to be discovered shortly and - hopefully ! - this one will be documented in more detail and preserved for posterity.

Update : November, 21th, 2006

Interestingly enough, there is another argentinian locality in the Nesquen province, where large blue celestite stalagtites are found, which closely resemble the Capillitas rhodochrosite stalagtites, but are of fine blue colour !

Update : January, 24th, 2007

German Mineralienatlas hosts an excellent description about the discovery of the Rhodochrosite stalagtites, which you can find here.

Update : May, 6th, 2007

A new publication online about the geology of Capillitas, please look here.

 

Capillitas Rhodochrosite in a nutshell :


Mineralogy :

Hydrothermal Pb - Zn Sulphide deposit with rich paragenesis. Much of the gangue consists out of manganese carbonate = rhodochrosite

Crystal Size :

The individual rhodochrosite crystals are rather small and seldom reach 1 cm size. The stalactitic aggregates may however reach several meter in length

Geology & Formation :

Hydrothermal sulphide / carbonate mineralisation

Current status :

The actual mining of lead and zinc sulphides stopped decades ago. However, rhodochrosite is actively mined for the use as carving stone and jewellery.

Remarks :

Probably the largest mass of rhodochrosite (in terms of tons) ever discovered.

 

Other notable & famous rhodochrosite occurences :

- Very large rhodochrosite crystals up to 20 cm size are known from the famous Mont. St. Hilaire alkaline pegmatites near Quebec, Canada.

- The famous Pasto Bueno deposit, Peru has produced some extradordinary rhomboedral rhodochrosites up to 15 cm.

- Worlds best and renowned rhodochrosite rhomboedrons up to 15 cm heve been mined until 2005 at the Home Sweet Home mine in Colorado, USA

- The Kalahari manganese fields in northern South Africa produced large amounts of splendid rhodochrosite clusters and individual crystals up to 6 cm or even larger, notably in the Hotazel and N'Chwaning II mine.

- Other famous rhodochrosite localities include the Uchuchacua Mine, Peru; various mines in Romania; the Chalkidiki mining district in Greece and the Wolf iron ore mine in Herdorf, Germany,

 

Massive rhodochrosite stalactites up to 0,5 m thickness and 3 m length, Capillitas vein

Photo Source : J.A.Saadi

 

Typical polished slab of rhodochrosite from Capillitas and some carved items
Source : Giant Crystal Project, seen in Edelsteinmuseum Idar Oberstein

 

Detail of a polished stalagtite, which formed from three individual "cores"
Source : Giant Crystal Project, seen in Edelsteinmuseum Idar Oberstein

 

Resources and relevant weblinks :

For more information on the mineral rhodochrosite please look at www.mindat.org, Webmineral and the german Mineralienatlas, which also have an excellent special "Mineral Portrait" about rhodochrosite here.

Though rhodochrosite from Capillitas is very well known and widespread, relatively little good background information is available. One of the best papers about the rhodochrosite - not the deposit as such - was published in the german mineral magazine Lapis in November 2000 :

LIEBER, W. (2000) Einmalige Tropfsteinbildungen aus Argentinien : Rhodochrosit - Stalaktiten
(Unique stalagititic formations from Argenita : Rhodochrosite - Stalagtites)
Lapis, 11, Vol. 25, 2000. pp. 13 - 20

Another good online publication (with english summary) about Capillitas is ZAVALIA, M.F.M. (1997 ?) : Mina Capillitas, un deposita epitermal del Noroeste Argentino, which you can find here and which also gives further literature about Capillitas.

There is also a german website, which deals with the splendour of rhodochrosites in general and gives some detailed information about the geology and discovery of the large rhodochrosite cave displayed above, which you can find here.

 

 

 

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