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29th Jul 2013 05:50 UTCNicu Pascanu Expert

French occurrences for Halotrichite

Hi everyone !

The only Mindat locality mentioned for Halotrichite, in France, is N164 By-pass, Caurel, Brittany. I've found also mentioned the following French occurrences:

-Granite quarry, Vieille-Brioude, Auvergne

-Huelgoat, Finistere

I own several Halotrichite specimen, there are the following labeling: Fumay, Champagne-Ardenne (attached photos).

Could someone give additional information about French occurrences of this mineral ?

Nicu

29th Jul 2013 15:14 UTCVik Vanrusselt Expert

Hello Nicu,

http://rruff.info/doclib/hom/halotrichite.pdf mentions Poullaouen (http://www.mindat.org/loc-59139.html)

Other localities in France can be found here: http://www.mindat.org/minlocsearch.php?frm_id=mls&cform_is_valid=1&cf_mls_page=1&minname=halotrichite&region=france

Vik

29th Jul 2013 17:59 UTCNicu Pascanu Expert

Hello Vik,

Are particularly useful your info sent. However, there is no reference to the Ardenne Dep.

I should review the other mineral present. And the Fumay locality, as well.

Thanks also !

Kind Regards,

Nicu

3rd Apr 2016 09:58 UTCVik Vanrusselt Expert

Hello Nicu et al.,

I've found another specimen of Halotrichite from "Anchamps, France" in an old micromount collection I recently acquired.

I've added the locality here: http://www.mindat.org/loc-270153.html

but I cannot find any references for the occurrence of Halotrichite there.

Any help?

Thanks,

Vik

3rd Apr 2016 10:50 UTCTimothy Greenland

Hello Nicu and Vik,

Fumay was a famous producer of slate for tiling for a very long period, finishing in the 1930s. The Ardennes museum apparently has specimens from the region including gypsum and 'iron ores'. I cannot find any details of theses specimens and have never (yet) visited that museum - but it looks as though the occurrence might well be possible... Anchamps had a stone quarry said to produce a porphyry-like and dioritic rock which was transported on flat-bottomed barges on the Meuse river... The two localities have differences in their characters but are in the Meuse valley. An efflorescence of halotrichite seems quite possible and might well have escaped 'official' attention!

Hope this helps

Tim

3rd Apr 2016 11:45 UTCAlfredo Petrov Manager

Efflorences of a big variety of Fe sulphate species are common wherever pyrite-bearing black shales (called by their german name vitriolschiefer, even in english) are exposed to weathering, especially when there are overhangs that protect the exposure from rain. I would guess that thousands of such vitriolschiefer localities are not on Mindat yet. Add some, Vic! :)-D

3rd Apr 2016 15:38 UTCErik Vercammen Expert

Black shales contain a lot of carbon, that give them their color. That carbon comes from organic debris in the mud of a sea, from which the shales are formed by metamorphosis. Organic debris also contain sulfur, and that reacts with iron, that is nearly omnipresent: pyrite is formed, and that tends to form cubic crystals during the metamorphosis.

When the layers are brought to the surface by the erosion, the pyrite is oxidized by water loaden with oxygen,and the formation of ironsulfates starts.The formed sulfuric acid can react with the shale minerals, so that alum is formed. This type of rock is rather common, and the name 'ampelite' has been used for them.

4th Apr 2016 18:55 UTCNicu Pascanu Expert

Hello Vik, Timothy, Alfredo and Erik,

Friendly thanks for the reminder-answer to Fumay's Halotrichite question.

During this time I've been trying to find out more details about their possible occurrence. I understand that these specimens were purchased from a Belgian stock market. Therefore, I assume that the locality can not be quite so covered by ''official'' fog. As mentioned just before, I totally agree that this hydrated sulfate can be formed in specified conditions. The same situation regarding the presence of Halotrichite in Romania, might say that this mineral species had not been mentioned before 2000 due its economical significance. But I found it in the past years to the northeast of Minei Hill, Baia Sprie, near of old weathered sulfide (pyritic) veins accompanied by instable melanterite.

I hope in a future update of the Ardennes localities data.

Best wishes,

Nicu

4th Apr 2016 20:49 UTCErik Vercammen Expert

The locality is now in Mindat (http://www.mindat.org/loc-270425.html) with some pictures. Can you upload your photo's please?

4th Apr 2016 21:37 UTCNicu Pascanu Expert

Thank you for the advice.

Some photos are presented in the start talk page. I will come back with several full-view photos for these specimens.

I haven't yet study the dark mineral associated with halotrichite.

The list minerals for Fumay locality is not yet available.

Best regards,

Nicu

5th Apr 2016 14:07 UTCErik Vercammen Expert

Nicu, I've have entered the mineral halotrichite at the Fumay-page, with your specimen as a reference.I don't know if you are a registerd Mindat-member yet: if so and you have asked the permission to upload minerals, please upload your pictures at the locality page. If you're not a member yet, you should become one to help build Mindat further.

5th Apr 2016 20:24 UTCNicu Pascanu Expert

Thank you Erik, I will done.

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