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Cesar M. Salvan
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Joined: 09 Jun 2008
Posts: 126
Location: Alcalá de Henares
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Posted: Mar 20, 2015 20:18 Post subject: The phurcalite from Assunçao mine (Ferreira de Aves, Satao, Portugal) |
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The center-north of Portugal hosts the richest pegmatite field in the Iberian peninsula. These pegmatites occasionally have a size and composition that makes them economically viable for the exploitation of some industrial minerals. The north Portuguese pegmatites are epigenetic and hosted by granites or metamorphic rocks (shales). They are Be, Nb-Ta, P and U rich pegmatites. The Assunçao mine is a good example of this type of pegmatite. It is a beryl-columbite-phosphate pegmatite, with a primary paragenesis where the big beryl crystals, the phosphates triplite, triphyllite, apatite and isokite, the columbite-Fe and copper sulfides are prominent minerals. A strong hydrothermal phase involved mobilization of Be with formation of secondary beryl and beautiful bertrandite, and alteration of primary phosphates. The remobilized phosphate left to the formation of good autunite specimens, thanks to the uranium richness of the deposit, and other secondary phosphates. The autunite, which generally forms beautiful crystals of yellow-green color, appeared initially in the market as uranocircite. We demonstrated, by analysis of a lot of specimens, that all these lots were autunite with high probability and the geochemistry of the pegmatite do not suggest an efficient barium source.
Now, in a recent study we performed on Assunçao samples, we can report the occurrence of phurcalite, an uranyl and calcium phosphate with different structure than autunite. Rarer than autunite, the phurcalite crystallized as a previous phase in the secondary assemblage of minerals in uranium-rich pegmatites. The phurcalite occurs as small spherules composed by the radial aggregation of acicular crystals and in the form of minute tabular crystals that resembles phosphuranilite, a mineral with similar distribution of uranyl cations in its structure.
It is possible that this mineral may have gone unnoticed due to its composition, similar to autunite, but it is easily distinguishable by morphology and by structural analysis, specially vibrational spectroscopy (Raman), the best tool to recognize the mineral.
In conclusion, another mineral species to add to the long list of the Assunçao mine.
Mineral: | Phurcalite and Autunite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Phurcalite (canary yellow spherules) and autunite (yellowish green crystals) on quartz. The specimen shows clearly the difference between the two mineral species |
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26348 Time(s) |
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Mineral: | Phurcalite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Dimensions: | FOV 2 mm |
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26315 Time(s) |
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Mineral: | Autunite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Dimensions: | FOV 0.8 cm |
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26366 Time(s) |
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Raman spectrum of the Assunçao phurcalite |
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26313 Time(s) |
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Mineral: | Phurcalite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Dimensions: | FOV 1mm |
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26337 Time(s) |
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Jordi Fabre
Overall coordinator of the Forum
Joined: 07 Aug 2006
Posts: 4896
Location: Barcelona
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Posted: Mar 21, 2015 07:40 Post subject: Re: The phurcalite from Assunçao mine (Ferreira de Aves, Satao, Portugal) |
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Superb. Thanks Dr.!
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Cesar M. Salvan
Site Admin
Joined: 09 Jun 2008
Posts: 126
Location: Alcalá de Henares
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Posted: Mar 22, 2015 13:12 Post subject: Re: The phurcalite from Assunçao mine (Ferreira de Aves, Satao, Portugal) |
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Thanks Jordi! A pleasure to contribute.
Mineral: | Phurcalite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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26136 Time(s) |
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stef4412
Joined: 14 Apr 2013
Posts: 11
Location: Embrun
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Posted: Mar 22, 2015 14:59 Post subject: Re: The phurcalite from Assunçao mine (Ferreira de Aves, Satao, Portugal) |
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Very nice
Thank a lot
It"s interesting to see phurcalite from this locality, it's changing from autunite alone
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Cesar M. Salvan
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Joined: 09 Jun 2008
Posts: 126
Location: Alcalá de Henares
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Posted: Apr 16, 2015 10:37 Post subject: Re: The phurcalite from Assunçao mine (Ferreira de Aves, Satao, Portugal) |
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More specimens to add to this interesting locality!
Mineral: | Phurcalite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Dimensions: | FOV 2 mm |
Description: |
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25652 Time(s) |
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Mineral: | Autunite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Dimensions: | FOV 1 cm |
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25657 Time(s) |
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Mineral: | Phurcalite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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25674 Time(s) |
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Mineral: | Autunite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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25663 Time(s) |
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Mineral: | Metatorbernite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Dimensions: | FOV 5 mm |
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25719 Time(s) |
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Mineral: | Mrazekite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Dimensions: | FOV 1.5 mm |
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25702 Time(s) |
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Mineral: | Columbite-Fe |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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The Assunçao pegmatites are rich in Nb. All the columbite/tantalite analyzed are clearly columbite-Fe |
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25760 Time(s) |
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Mineral: | Torbernite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Dimensions: | Crystal 1.5 mm |
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25675 Time(s) |
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Mineral: | Autunite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Dimensions: | FOV 5 mm |
Description: |
Autunite photomicrograph under UV light. |
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25786 Time(s) |
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Roger Warin
Joined: 23 Jan 2013
Posts: 1176
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Posted: Apr 16, 2015 12:57 Post subject: Re: The phurcalite from Assunçao mine (Ferreira de Aves, Satao, Portugal) |
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Hi,
Many thanks. A master class with great pictures of exceptional minerals.
Roger
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Cesar M. Salvan
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Joined: 09 Jun 2008
Posts: 126
Location: Alcalá de Henares
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Posted: Apr 16, 2015 20:18 Post subject: Re: The phurcalite from Assunçao mine (Ferreira de Aves, Satao, Portugal) |
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Thanks Roger!
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Cesar M. Salvan
Site Admin
Joined: 09 Jun 2008
Posts: 126
Location: Alcalá de Henares
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Posted: May 04, 2015 18:50 Post subject: Re: The phurcalite from Assunçao mine (Ferreira de Aves, Satao, Portugal) |
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Adding more complexity to the uranyl phosphates from Assunçao mine. The saleéite was not previously observed in the deposit, but we found very interesting specimens of saléeite-torbernite intergrown. The saleéite shows greenish yellow to green color, depending on the copper content. The torbernite forms epitaxial intergrowhts and alternating layers with saléeite. The most interesting specimens forms beautiful centimetric crystal aggregates on partially dissolved autunite or covering previous autunite crystals. Occasionally, a later autunite generation crystallized out on previous saléeite-torbernite.
So, the current count of identified uranyl phosphates described in this thread is: phurcalite, autunite, saléeite and torbernite. The observation of specimens suggests an early phurcalite deposition followed by autunite and later saléeite/torbernite. Also, the intergrowths and partially dissolved or attacked crystals suggests remobilization and recrystallization processes.
The uranyl phosphate minerals from Assunçao mine are very interesting and beautiful. Unfortunately the minerals are isostructural and practically indistinguishable de visu. Apart of torbernite, the identification of these species always require an analysis of every specimens. The Raman spectroscopy is a fast and non destructive tool to test them and we regularly used it in all samples.
Mineral: | Torbernite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Dimensions: | FOV 5 mm |
Description: |
Tabular crystals of dark green torbernite on quartz. |
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25187 Time(s) |
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Mineral: | Saléeite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Dimensions: | FOV 1.2 mm |
Description: |
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25175 Time(s) |
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Mineral: | Saléeite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Dimensions: | FOV 1.2 cm |
Description: |
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25236 Time(s) |
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Mineral: | Saléeite and Torbernite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Dimensions: | FOV 1.2 cm |
Description: |
Torbernite overgrown on saléeite |
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25198 Time(s) |
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Mineral: | Saléeite and Torbernite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Dimensions: | FOV 1.2 cm |
Description: |
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25354 Time(s) |
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yowanni
Joined: 27 Feb 2008
Posts: 37
Location: Spain (Cantabria / Madrid)
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Posted: May 05, 2015 01:19 Post subject: Re: The phurcalite from Assunçao mine (Ferreira de Aves, Satao, Portugal) |
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Great photos and very interesting information. Thanks for posting!!
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Cesar M. Salvan
Site Admin
Joined: 09 Jun 2008
Posts: 126
Location: Alcalá de Henares
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Posted: Jan 11, 2016 16:15 Post subject: Re: The phurcalite from Assunçao mine (Ferreira de Aves, Satao, Portugal) |
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More minerals from this interesting deposit
Mineral: | Bertrandite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Dimensions: | Xtal 2 mm |
Description: |
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22960 Time(s) |
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Mineral: | Bertrandite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Dimensions: | FOV 5 mm |
Description: |
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22967 Time(s) |
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Mineral: | Uraninite, Schoepite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Dimensions: | FOV 1 cm |
Description: |
Uraninite with "gummites", formed by schoepite, becquerelite and an still undetermined Bi+U mineral |
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22949 Time(s) |
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Mineral: | Becquerelite |
Locality: | Senhora da Assunção Mine, Aldeia Nova, Ferreira de Aves, Sátão, Viseu District, Portugal | |
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Dimensions: | FOV 0.5 cm |
Description: |
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22900 Time(s) |
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Mineral: | Torbernite+Saléeite |
Dimensions: | FOV 1 cm |
Description: |
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22948 Time(s) |
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