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Ajoite

Posted by Rock Currier  
avatar
Rock Currier January 22, 2009 09:12AM
This article has been prepared for the Mindat Best Minerals project. The aim of this project is to present information on important localities and specimens for each mineral specie. As new finds are made and new knowledge is made available the individual articles will be revised to include this information. Readers are encouraged to contribute by posting a response in this thread. All revisions will be stored, thus ensuring traceability and availability of previously included information. A complete list of articles can be found in the list of finished Best Minerals articles. To cite this version: Currier, R., Revheim O. (2016): Ajoite. revision 2.1 Mindat Best Minerals Project, article "mesg-66-124530". Please be advised that the photos cannot be used without the consent of the copyright holder

Ajoite



(K,Na)Cu72+AlSi9O24(OH)6.3H2O

Triclinic




Ajoite is found at 12 localities registered in Mindat (December 2015). This number would undoubtedly be significantly higher if all localities near Musina were not lumped into a single locality. It is also quite possible that a more thorough review of light bluish secondary copper minerals labeled "chrysocolla" would reveal more ajoite localities.

The structure of ajoite was solved by Pluth and Smith (2002), who found that the mineral consists of zeolite-like cage structures alternating with octahedral CuO6 layers. The chemical formula of ajoite indicates some replacement of Na for K, and in microprobe analyses on material from Ajo, a Na:K ratio of 1:3 has been presented. The Musina localities have a strong Na enrichment with increasing alteration, and it would be interesting to see if a possible Na-dominant ajoite might exist in this material.

The two most prominent ajoite localities are the Ajo district of Arizona, USA and the Musina (Messina) district of South Africa. These are also the specimens of most interest to collectors. In particular, the ajoite-included quartz crystals from the Musina district are popular. They are also highly regarded by those believing in the metaphysical properties of ajoite, as there are seemingly no limits to the amount of success and good health that will come your way if you purchase an overly prized ajoite-included quartz crystal! On the good side, this market provides a good incentive for specimen mining, since a high demand and limited supply provide a favorable market for those who have ajoites to sell. The downside of this is the temptation to apply false labelling; chrysocolla-included quartz is known to be sold as ajoite.

Individual crystals of ajoite up to about a half millimeter are known. Perhaps of most interest to collectors are the specimens of quartz from South Africa with inclusions of ajoite that give them a pleasing blue color. There are other localities with better crystals, but these tend to be of more interest to micromount collectors and mineralogists than quartz with inclusions of ajoite.


Democratic Republic of Congo (Zaïre),
Katanga (Shaba), Katanga Copper Crescent, Kakumba, Luputo

The Luputo mine was opened in 2007 and produced 2400 tons of copper in 2008. Some specimens have appeared on the international mineral market. a small number of these has been labelled ajoite, but further investigations confirm that they are chrysocolla. No ajoite has been identified from Luputo, see http://www.mindat.org/forum.php?read,9,377662,379189#msg-379189 for further details.


Ajoite,
South Africa,
Limpopo Province, Vhembe District, Musina (Messina), Messina Mine, No. 5 shaft

Ajoite in Quartz, 2.4 cm tall
Ajoite in Quartz, xl 12 cm across
Ajoite in Quartz, 2.4 cm tall
Ajoite in Quartz, xl 12 cm across
Ajoite in Quartz, 2.4 cm tall
Ajoite in Quartz, xl 12 cm across
Ajoite in Quartz, 7 cm specimen
Ajoite phantom in quartz, 17 mm FOV
Ajoite in Quartz, 7 cm specimen
Ajoite phantom in quartz, 17 mm FOV
Ajoite in Quartz, 7 cm specimen
Ajoite phantom in quartz, 17 mm FOV
Ajoite in Quartz, 4.7 cm tall
Ajoite in Quartz, 3.6 cm tall
Ajoite & Papagoite, 3 cm tall
Ajoite in Quartz, 4.7 cm tall
Ajoite in Quartz, 3.6 cm tall
Ajoite & Papagoite, 3 cm tall
Ajoite in Quartz, 4.7 cm tall
Ajoite in Quartz, 3.6 cm tall
Ajoite & Papagoite, 3 cm tall
Ajoite in Quartz, 4 cm FOV
Ajoite in Quartz, 4 cm FOV
Ajoite in Quartz, 4 cm FOV
Ajoite in Quartz, 4 cm FOV
Ajoite in Quartz, 4 cm FOV
Ajoite in Quartz, 4 cm FOV


The Messina copper ores were exploited by both Bantu and pre-Bantu tribes, and rumors of abandoned workings attracted an exploratory party led by Colonel J.P Grenfell. Based on his assessment of the ore and its potential, he formed Messina (Transvaal) Development Company (Messina Ltd from 1950). Industrial mining commenced in 1906, and when the last of the mines were closed in 1992, a total of 40 million tonnes of copper ore with an average copper content of 2% had been produced. As a point of interest it should be mentioned that, before he became US President, Herbert Hoover was a member of the board from 1914 to 1916.

The main specimens produced from the Musina area are quartz crystals, but quartz crystals containing inclusions of copper minerals are more attractive and such specimens have been known in the USA since the early 1950s. They were imported to the USA by George Burnam, a mineral dealer in Monrovia, California, and which he acquired during his round-the-world trip with Jack Jago in 1950. These early crystal samples were said to have ajoite inclusions, but most of these contained dark blue inclusions of papagoite and some red colored cuprite. The quartz crystals with light blue ajoite inclusions were mostly found in July 1985 and are much sought after by collectors. The majority of specimens are individual loose crystals in thumbnail to miniature sizes. Some larger groups were also found: the largest and finest single crystal specimen consists of an undamaged quartz crystal 25 cm long, rimed at the base by smaller quartz crystals also containing ajoite.

After the mines closed in 1992, sporadic specimen mining has delivered specimens to the world market. In rare cases, large spectacular specimens have been retrieved. Some large plates with ajoite-included quartz crystals were found throughout the 1990s, but the most spectacular crystal group was found in 2007 - the "Artonvilla cluster", a 400 kg specimen with ajoite-included crystals up to 30 cm. It was found by Wynand and Gelden Kuypers, who had been operating a mine on the Artonvilla farm specifically to recover specimens. The Artonvilla cluster was recovered in November 2007 from a relatively shallow pocket in a previously un-mined area, about 10 m below the floor of the open pit and about 40 m north of the main Artonvilla shaft. The cluster was located in the roof of the pocket with only a few small quartz crystal tips protruding. Approximately 40 tonnes of granite was taken out from around the cluster after which it was broken from the roof of the tunnel using pit props and a 20-tonne hydraulic jack and gradually lowered and turned over– a process that took over four weeks. The specimen was carefully cleaned and trimmed down to a smaller specimen weighing roughly 400 kg and measuring 135x90x60 cm. It was presented at the Denver show in 2012 (a rather hefty transport from South Africa) but despite these efforts it proved impossible to sell and was eventually split into about 20 smaller pieces.

The Artonvilla cluster
The Artonvilla cluster
The Artonvilla cluster



In terms of geology, the Messina copper deposits comprise an important group of breccia pipes, disseminated replacement and vein deposits emplaced in granulite facies metamorphic rocks of the Limpopo mobile belt. Apparently the deposits were structurally controlled, thus the structures acted as channels for the mineralized hydrothermal solutions. Sulphide mineralization mainly took place within the crystallizing quartz veins. The orebodies reveal a distinct oncentric zonation of hydrothermal minerals from an outer zone of sericitization, followed inward by zones of albitization, chloritization and epidotization. Also, the sulfides show a zonation from an outer pyrite, through chalcopyrite and bornite, to chalcocite and occasional native copper zones at the center.

Chemically, the most important changes are related to the increase in the K2O content of the sericite-bearing outer aureole and the sharp decline of this component as well as SiO2 with increasing alteration. The abundance of Al2O3 and Na2O increases with advancing states of alteration. The initial hydrothermal fluid entered the structural traps at elevated temperatures, probably in excess of 650o C, and passed through the rocks down a temperature gradient, finally cooling to about 400o C at the outer extremity. The remaining trapped solutions cooled inward in much the same fashion as pegmatites do, thereby creating the well developed mineral zonation. The central parts of the orebody indicate mineral associations compatible with temperatures in the range of 140o C to 280o C. The low temperature is combined with a favorable chemistry containing Cu and SiO2.


Ajoite,
USA,
Arizona, Pima County, Ajo District, Little Ajo Mts., Ajo, New Cornelia Mine (Ajo Mine)

Ajoite, FOV ~5 mm.
Ajoite, FOV 2.5 mm
Ajoite, FOV ~5 mm.
Ajoite, FOV 2.5 mm
Ajoite, FOV ~5 mm.
Ajoite, FOV 2.5 mm
Ajoite & Olivenite, FOV 1.9 mm
Ajoite & Olivenite, FOV 1.9 mm
Ajoite & Olivenite, FOV 1.9 mm
Ajoite, FOV 5 mm
Ajoite & Shattuckite, 47 mm
Ajoite, FOV 5 mm
Ajoite & Shattuckite, 47 mm
Ajoite, FOV 5 mm
Ajoite & Shattuckite, 47 mm


Native Americans had long mined surface exposures of copper veins near the New Cornelia site for pigments: red copper oxide and green copper carbonate. Spanish miners are known to have excavated test shafts in the area by 1750, but the amount of copper produced is not known. Americans claimed the location in 1854 and shipped a few loads of selected ore to Swansea, Wales (U.K.), but high transportation charges left little or no profit, and the mine was abandoned. Full-scale mining using steam shovels was started in 1917, making the New Cornelia the first large open pit mine in Arizona. Mining and treatment of the underlying but lower grade copper sulfide orebody began in 1924. The mine was shut down in 1983 due to low copper prices and a dispute with the local labor union. Since the closing of the mine, it has been worked for specimens but, according to Reynolds (2015), the pit is currently caved in and offers no good collecting opportunities.

The Ajo mining district is a collage of different types of ore minerals, altered rocks, and plutons of Precambrian, upper Mesozoic (Laramide), and middle Cenozoic age. The Ajo porphyry copper deposit (65-63 Ma) is localized in the porphyry phase of the granodiorite of the Cornelia Pluton.

Several alteration processes have been at play in this rock sequence, and at least two stages of supergene alteration and enrichment are documented in the New Cornelia deposit. Remnants of a chalcocite blanket are preserved at the south end of the pit, derived from supergene destruction of chalcopyrite and bornite, and a second supergene event affected the rocks within several hundred feet of the original ground surface in the pit area. Altered rocks have been converted to masses of clay, sericite, hematite, saussurite, and copper oxides. The copper oxides formed the main ore produced in the initial phases of development. Dating by Cook (1995) on New Cornelia alunite veins demonstrates relatively young ages of 11 and 2.2 Ma for this second stage of supergene development. Ajoite and papagoite were discovered in this ore.

Schaller and Vlisidis (1958), in their type description, give the following discription of the occurrence of ajoite, and the history behind the first find of the mineral: "Specimens of a bluish-green copper aluminum silicate, named ajoite after the locality Ajo in northwestern Pima County, Arizona, were collected by Harry Berman of Harvard University in August 1941, together with specimens of dark blue shattuckite. Preliminary examination by him, chiefly optical, indicated that the greenish mineral was probably a new species. It had been planned by Berman and Schaller to collaborate on the study of this new mineral and possibly to extend such a collaborative investigations also to include all the known copper silicate minerals, a plan nullified by Berman's untimely death in 1944. It is a tribute to Berman's keen perception that his earlier prediction of a new mineral has been borne out.

Most of the ajoite is compact massive, resembling some deeper colored chrysoprase in color and specimen structure, and is intimately mixed with dark blue shattuckite and white massive quartz. Occasional small cavities contain aggregates of elonaged plates of ajoite, a millimeter and less in length. Other less abundant associated minerals observed are minute pearly scales of sericite, white powdery quartz, pyrite, very pale blue altering shattuckite, limonitic stains, and on one specimen massive conichalcite."


The authors discuss in detail the difference between ajoite and other Ca- and Al-bearing silicates, including several varieties of chrysocolla and clay minerals. That ajoite justifies its species status is confirmed by Kato and Miura (1976), Chao (1981) and Pluth and Smith (2002), who respectively found the cell dimensions, provided more detailed chemical, crystallographic and optical data and solved the structure of ajoite.

Chao (1981) provides an interesting description of the specimen he worked on, possibly indicating two different parageneses for ajoite within the same alteration zone:

"The bluish green ajoite occurs in veinlets and as sprays of fine, prismatic, bladed crystals lining irregular shaped vugs in monzonite stained in places by a mixture of hematite and sericite. Calcite crystals are common in the vugs and minor amounts of barite are noted. Shattuckite and conichalcite,reported to be associated with the type ajoite material are characteristically absent. The ajoite crystals are elongated along c and flattened on (010).{010} is the most prominent form and {100} and {1T0} are much less prominent but are always present. The termination on c may be either {001} or {203} or both."

It appears that both of these parageneses are represented with photos in the Mindat database.



References



Beale. C.O. (1985): Copper in South Africa-Part II, Journal of the South African Institute of Mining and Metallurgy, Vol. 85, No. 4, pp 109-124.

Cairncross, Bruce (1991): The Mesina mining district, South Africa, The Mineralogical Record, Vol. 22, No. 3, pp 187-199.

Chao, George Y. (1981): Ajoite: New data. American Mineralogist, Vol. 66, pp 201-203.

Cox, Dennis P., Force, Eric R., Wilkinson, William H., More, Syver W., Rivera, John S. and Wooden, Joseph L. (2006): The Ajo Mining District, Pima County, Arizona—Evidence for Middle Cenozoic Detachment Faulting,Plutonism, Volcanism, and Hydrothermal Alteration. USGS, Professional Paper 1733. 53 pages.

Gilluly, James (1946): The Ajo Mining District Arizona. USGS, Professional Paper 209. 136 pages.

Jacobsen, J.B.E. and McCarthy, T.S. (1976): An unusual hydrothermal copper deposit at Messina, South Africa (Abstract). Economic Geology Vol. 71, No. 1, pp 117-130.

Kato, Toshio and Miura, Yasunori (1976): Cell dimensions of ajoite. Short Communications, Mineralogical Journal, Vol. 8, No. 4, pp 234-239.

McKenzie, Ronnie (2013): The Artonvilla cluster, large Messina quartz with ajoite (brochure). 4 pages.

McKenzie, Ronnie (2015): Personal communication.

Mundalamo, H.R. and Ogola, J.S. (2012): Messina copper sulphide deposits revisited: Geological and structural study of the deposits (abstract): SGEM2012 Conference Proceedings Vol.1, pp 399-408.

Pluth, Joseph J. and Smith, Joseph V. (2002): Arizona porphyry copper hydrothermal deposits II: Crystal structure of ajoite, (K,Na)sub>3Cu20Al3Si29O76(OH)16 - 8H2O. Proceedings of the National Academy of Sciences. Vol. 99  No.17, pp 11002-11005.

Reynolds, Eugene (2015): Mindat message board.

Sawkins, F.J. (1977): Fluid inclusion studies of the Messina copper deposits, Transvaal, South Africa, (Abstract). Economic Geology Vol. 712, No. 4, pp 619-631.

Schaller, W.T., and Vlisidis, Angelina C. (1958): Ajoite, a new hydrous aluminium copper silicate. The American Mineralogist, Vol. 43, pp 1107-1111.

Thomas, William J. and Gibbs, Ronald B. (1983): Famous Mineral Localities: The New Cornelia Mine, Ajo, Arizona.The Mineralogical Record. Vol. 14, No. 5, pp 283-298.

USGS (2011): Minerals Yearbook, 2009, Vol. 3, Area Reports, International, Africa and the Middle East. 376 pages.

Wikipedia.

Mindat mineral and locality Pages

RevisionHistory

Revision no date description editor
1.0 2009 First Draft Rock Currier
1.1 2010 Reformatted Rock Currier
1.2 2011 Added mineral description Rock Currier
2.0 2015 Rewritten and reformatted Olav Revheim
2.1 2016 removed Luputo entry as ajoite from here was erroneously reported


Reviewed by Becky Coulson Dec 2015.



Click here to view Best Minerals A and here for Best Minerals A to Z and here for Fast Navigation of completed Best Minerals articles.

Rock Currier
Crystals not pistols.



Edited 40 time(s). Last edit at 03/31/2016 02:20PM by Olav Revheim.
avatar
Marketa Tumova February 17, 2011 01:46PM
My father loves Ajoites and I have seen a really big Quartz (about 1m high) with Ajoite inclusions from area around Mesina. The picture is not mine, I have to ask the owner of this picture if I can share it. But it is unbelievable.
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Rock Currier February 18, 2011 02:27AM
Marketa,
We would love to put a picture of the big Quartz and Ajoite in the Best Minerals article if you can get one uploaded to the Mindat gallery.

Rock Currier
Crystals not pistols.
avatar
Rock Currier November 08, 2013 11:54PM
Matthew,
The picture of quartz you display above is somewhat over exposed, or at least it appears that way on my monitor.

Rock Currier
Crystals not pistols.
avatar
Bruce Cairncross August 06, 2015 12:55PM
Messina No. 5 Shaft specimen collected in the late 1980s. Quartz, ajoite, chlorite iron-rich albite. 64mm X 44mm. Bruce Cairncross specimen and photo.

avatar
Adam Kelly August 17, 2015 01:22AM
I hate to knit-pick but the "ajoite" above 4.9cm across, 4th photo down from the top, sure looks like papagoite.
I know it's hard to tell from photos, but I'd bet on it.
AK
avatar
Debbie Woolf August 17, 2015 01:53AM
I agree Adam, it's also listed as papagoite!

Rock, note the Messina mine locality has recently changed.
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Rock Currier August 19, 2015 01:16AM
Debby & Allen,
I have removed the image from the article, and added the current improved localiy. But would bet a stake dinner that it was labeled Ajoite when it was originally chosen for the article. Reviewing our Ajoite images it would appear that subsequent to the creation of the article other new Ajoite images from this locality should be chosen or added to the article.

Rock Currier
Crystals not pistols.
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Doug Daniels August 19, 2015 04:32AM
Rock - a "stake" dinner? Do you suspect some vampires amongst us? :-D
avatar
Rock Currier August 20, 2015 09:01AM
Yes, but probably no more than a dozen. But that's why I keep my Kongsberg's close at hand in case I have to melt them down into bullets.

Rock Currier
Crystals not pistols.
avatar
Olav Revheim December 09, 2015 06:46PM
I have started the tedious process of fixing the picture format for these articles, and I realize that a large number of new photos have been added to the database since the article was done in 2011. I will appreciate if someone could find the time to prepre a list of photos and localities that should be included in this article.

Any additional information on any of the localities and finds will also be appreciated.

Olav
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eugene reynolds December 09, 2015 07:22PM
hi all,,,,
several years ago, I was with a small amount of members from m.s.s.c. that were invited to collect in the new cornelia pit in ajo.. we collected on several locations on 4,5 benches and we all had great luck in collecting,almost all of the minerals that were mined from the pit ... all were micros,but of fine quality..

the ajoite & papogite were found in the middle of the pit,,about 100,200, feet below the serface. this area is now nothing but space,,(BOO HOO ),, no more of these two minerals will be ever found at the mine,, I stoped by the mine this year coming back from Tucson,,, the pit is now in total cave in.. the pit is now closed to any & all collecting,,, rats!!!! Eugene reynolds
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David Von Bargen December 09, 2015 07:57PM
http://www.mindat.org/photo-578642.html
http://www.mindat.org/photo-672223.html Luputo, Kakumba, Katanga Copper Crescent, Katanga (Shaba), Democratic Republic of Congo (Zaïre)

Not much has changed in the last few years. You basically have quartz included crystals from SA and micros from Ajo.
avatar
Olav Revheim December 10, 2015 07:15AM
Eugene and David

Thanks!

Olav
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Paul De Bondt December 10, 2015 11:24AM
David and Olaf

I would wait with the Lupoto or Luputo or Loputo ajoite as this is the only posted specimen and that all the others are labeled chrysocolla:-S
I am not sure this is ajoite.

And there are 2 almost the same registrations on Mindat in 2 different districts.
http://www.mindat.org/loc-228194.html and http://www.mindat.org/loc-159574.html
I think the second is wrong.
If one clicks on the wicki link and open the Kalumines link, one can see the quartz crystals from the wrong locality on Mindat.:-S

I hope this helps.

Paul.
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Olav Revheim December 10, 2015 11:55AM
Thanks Paul,

Did you see the caption on Luputo specimen? It states that the specimen has been analysed. I have contacted the uploader for details.

http://www.mindat.org/photo-672223.html

Olav
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Paul De Bondt December 10, 2015 12:02PM
No problemo Olav.

Yes I saw that and it would be great to see the analysis results.

The link you have send me shows no image ..... a bug prehaps ???

Paul.
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Olav Revheim December 10, 2015 12:05PM
Thanks Paul.

The missing photo in the link is interesting. If you click on the bottom arrow in the window, you will see the caption and the child photos, but if you click on ny of the child photos, the url changes but still no photo is shown. :-S

Olav
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Debbie Woolf December 10, 2015 04:47PM
I used the right sided arrow to view the other photos and then the main photo opened :-S
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