Armstrongite

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Can you help make this a better article? What good localities have we missed? Can you supply pictures of better specimens than those we show here? Can you give us more and better information about the specimens from these localities? Can you supply better geological or historical information on these localities?

Below are some preliminary notes I have made about Armstrongite. This entry and thread has been made as a place holder for information that you will hopefully contribute about Armstrongite. It should be in no way be thought of as a claim I have staked out to write about this mineral, and in fact is an invitation for someone to step forward and create the article about this mineral. If you are so inclined and have questions about the format that such an article should have, go the The welcome topic at the top of the Best Minerals forum and read what has been posted there. Also take a look at some of the more mature articles that have already been written like Rhodochrosite, Adamite, Millerite etc. You will need also to pick out other images of Armstrongite that will go into the article.



Armstrongite
CaZr(Si₆O₁₅)·3H₂O Monoclinic


*Armstrongite Rare species collections.
CaZrSi6O15·2.5H2O

Mongolia,
Khan-Bogdinskii Massif. “The mineral occurs in poikilitic crystals up to 2 cm in size and in aggregates up to 50 x 50 cm in schlieren of alkali granite pegmatite of the Khan-Bogdinskii massif…which are at the contact of arfvedsonite granite with xenoliths of acid volcanic rocks. The pegmatite consists of quartz, microcline, albite, aegirine, and arfvedsonite, with accessory monazite, synchysite, sphene, and titano-silicates. These are not freestanding crystals. I have never seen any specimens that look much different than a common rock to the average person. The name is for Neil A. Armstrong, American astronaut, first man on the moon’s surface.”1
1 American Mineralogist, Vol.59, 1974, p 208.

Also armstrongite is known in Canada, on the Quebec-Labrador boundary, in peralkaline granites of the Strange Lake complex southeast of Lac Brisson .



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Rock Currier
Crystals not pistols.



Edited 3 time(s). Last edit at 12/27/2012 08:31AM by Rock Currier.

Only the single 50x50 cm block of armstrongite was extracted from Dorozhnyi pegmatite. From this time nobody saw coarse-crystalline armstrongite from the massif similar to [www.mindat.org]. Usually its specimens from the later finds looks like [www.mindat.org].

In the center of the photo above, you can see free-standing (almost vertical) terminated crystal from cavity in massive coarsecrystalline armstrongite aggregate of the same initial 50x50 cm its block (by the way, apparently all this block is the holotype for the specie, and its parts are parts of holotype). Two more crystals are right under it (almost horizontal). These are the single armstrongite crystals which I sometimes saw. Its elongated monograins may be 2-3 cm long, but without crystal faces.

On Strange Lake armstrongite is known only in accessory quantities, as minor component of alkaline granites with gittinsite mineralization. It is visible only in thin sections of such rocks.

Armstrongite formula is very similar to elpidite one. And initially it was considered as Ca-dominant analogue of elpidite. But later was found, that these minerals has different structures.

The story of armstrongite name is very funny.
Gagarinite was discovered in elpidite bearing alkaline granite massif Verkhnee Espe and was named in honor of the first cosmonaut Yurii Gagarin - [www.mindat.org]. Long time (up to begining of 80th) this was the single locality of gagarinite. Later it was found in significant quontities on Katugin deposit.
Massif Khan Bogdo was discovered on the boundary 60th-70th. This massif was very similar to Verkhnee Espe from many points of view - mineralogicaly,geochemicaly, geologicaly and by its age. So mineralogy of both massifs was very close. By the way, up to now only only 4 such type massifs are known (and 2 one are close, but don't investigated enough to be stated as the same type).
Mineralogist from Irkutsk Nikolai V. Vladykin had work on Khan Bogdo from the time of its discovery. Of course he wanted to find all minerals of Verkhnee Espe in this massif. And especially he wanted to found such important ore concentrator as gagarinite. He had looking for gagarinite in rocks and pegmatites of Khan Bogdo during some years without any success and became angry. He promised: "In case, if I don't found gagarinite before, the first new discovered mineral on the massif I'll name in honor of the first American cosmonaut!" Gagarinite wasn't found on Khan Bogdo, and now we know, why it was unable to be found here. And the first mineral discovered in Mongolia was named in honor of Neil Armstrong. Long time it was the single Mongolian mineral. But later Mongolite and Ferriallanite-(Ce) were found here. By the way, both are discovered in alkaline massifs the same type - with primary magmatic elpidite.

It is interesting, that zajacite-(Ce) - mineral very compositionally close to gagarinite-(Y) - recently was found in Strange Lake rocks together with armstrongite. Probability of find zajacite-(Ce) on Khan Bogdo is much more high, than gagarinite-(Y) find.



Edited 1 time(s). Last edit at 06/02/2009 08:38PM by Pavel Kartashov.