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Astrophyllite

Posted by Rock Currier  
avatar Astrophyllite
May 27, 2009 06:58AM
©


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This article is in a pre-construction phase.
Someone is needed to work on this article which contains a few preliminary notes.

1. The localities need to be brought into conformity with mindat locality strings if necessary, reversed and made bold.
2. If image links appear below they need to be embedded in the article. If none are present the Mindat image bank needs to be searched for images of this mineral and the better ones and their localities need to be placed in the article.
3. The captions for the images need to be added.
4. The images need to be tweaked so that they look nice. This last bit is tedious and requires patience and some little artistry.



Astrophyllite
(K,Na)3(Fe,Mn)7Ti2Si8O24(O,OH)7 Triclinic
A 1.8cm xl. of Astrophyllite on Albite, Poudrette quarry, Mont Saint-Hilaire, Québec, Canada


Astrophyllite Display collections?
(K,Na)3(Fe2+,Mn)7Ti2Si8O24(O,OH)7
There are a number of localities for this mineral and some produce lustrous brown crystal sprays in rock, often stellate, up to about 15 cm. There are many localities but few with free standing crystals. The free standing crystals are almost always rather rough. Found mainly in nepheline syenites, alkali granites, and their pegmatites but other occurrences as well.

Astrophyllite
Canada
Quebec, St. Hilaire A & B & C. The best crystals are probably found at St. Hilaire up to at least five cm in length. The crystals are somewhat prismatic lath-like or acicular and usually not very sharp or lustrous. They will be most appreciated by those collectors who have a thing for good crystals of minerals that rarely occur in good crystals. Fairly well formed crystals grow to be at least 5 cm long. These are not common. “Astrophyllite… is one of the more common and conspicuous minerals found at Mont St-Hilaire. It is found as well-formed, sharp, tabular to bladed crystals to several centimeters in length, as well as bladed and acicular microcrystals in pegmatite veins and pipes. It is also found very widely disseminated as flakes and bladed crystals or radiating crystalline masses embedded in nepheline syenite, in close proximity to various pegmatitic structures, and rarely in hornfels, marble xenoliths and miarolitic cavities. The color of astrophyllite is medium to dark brown, reddish bronze or brownish red. Some very small crystals are transparent to translucent while the large crystals and the embedded crystalline masses are opaque. The mineral is micaceous, with a greasy to pearly luster. Astrophyllite is practically identical in color and habit to kupletskite, with which it may be intimately associated; consequently, visual identification is unreliable.”1
1 Mineralogical Record, Vol. 21, 1990, p297-8.

Astrophyllite
Norway
Langesundfjord. I have also thrown in one picture of a specimen from Norway for a little perspective. The specimen pictured here is in the British Museum of Natural History and the brown crystal is about 3 cm in diameter. Certainly the museum in Copenhagen, Denmark has better ones. I don’t think they get as good as the ones from St. Hilaire.



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 3 time(s). Last edit at 12/27/2012 08:07AM by Rock Currier.
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