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Techniques for CollectorsPreservation of Laumontite

29th Jan 2019 18:55 GMTEric He

I have a specific area in mind that could have potential for very good Laumontite crystal groups. I've heard that they are extremely prone to "drying out" and crumbling to bits, so I am asking for help on any ways to maintain/preserve Laumontite in a display cabinet/perky box, just like any other mineral(not in a tub of water). I was thinking perhaps coating it in mineral oil would keep the moisture in?


Thanks, Eric

29th Jan 2019 19:22 GMTJolyon Ralph Founder

No, the only safe way to keep laumontite is to keep it under water, or ensure it is always kept between 0 C and 12 C, as in that temperature range it won't dehydrate.


Even if you coat the crystals with oil it will still dehydrate. There's a reason that most people don't have laumontite crystals in their collections.

29th Jan 2019 19:51 GMTKelly Nash Expert

The only ones I've seen that have lasted for some time were soaked in a thin solution of white glue. But the solution doesn't penetrate very far, so they are still very fragile.

29th Jan 2019 21:07 GMTRichard Gunter Expert

There is an occurrence of laumontite that does not dehydrate. The Dankoe Mine, British Columbia, has non-dehydrating laumontite occurring with acanthite and native silver on late-stage, bladed, colourless calcite crystals. It was originally considered to be scolecite but was found to be laumontite by U.B.C.

29th Jan 2019 21:28 GMTHerwig Pelckmans Expert

So who can answer the obvious question?


Cheers, Herwig

Herwig Pelckmans

MKA (Min.Soc.Antwerp), Belgium

29th Jan 2019 21:37 GMTJolyon Ralph Founder

Obviously it's not laumontite :)

29th Jan 2019 21:41 GMTRichard Gunter Expert

Hi Jolyon and Herwig:


This has been analyzed by XRD as laumontite so if it is not laumontite it has the same XRD trace. There may be something else going on here but it appears to be laumontite.

29th Jan 2019 22:09 GMTJolyon Ralph Founder

So, there is one sensible possibility, and that it is what was previously called "primary leonhardite", which is essentially the material that laumontite dehydrates into.


"This “primary leonhardite,” with more than five channel cations pfu, neither dehydrates nor rehydrates at room temperature. The excess of channel cations compared with ordinary laumontite indicates that “primary leonhardite” has additional non-framework cation sites (Baur et al., 1997; Stolz and Armbruster, 1997) occupied by H2O molecules in fully hydrated laumontite. This also explains why “primary leonhardite” cannot be further hydrated and why it shows no indication of weathering as usual for exposed laumontite. The species name “leonhardite” was recently discredited as a mineral species (Coombs et al., 1997; Wuest and Armbruster, 2000), because “leonhardite” is just a partially dehydrated variety of laumontite."


Ref: http://www.iza-online.org/natural/Datasheets/Laumontite/Laumontite.html

29th Jan 2019 22:11 GMTJolyon Ralph Founder

Wondering why this was discredited but metatorbernite hasn't been. I'm sure there's a difference that someone can point out!

29th Jan 2019 22:25 GMTRichard Gunter Expert

So is the Dankoe Mine material true laumontite or "metalaumontite" in concordance with torbernite-metattorbernite etc. As far as I know there is no XRD difference between torbernite and metatorbernite. Metatorbernite at Musonoi Mine is transparent and non-dehydrated and the Dankoe Mine laumontite has a similar appearance.

30th Jan 2019 14:43 GMTTimothy Greenland

Hello Jolyon,


The laumontite (with epidote) I collected from Moon's Hill Quarry, Stoke-St-Michael, Somerset back in April 1962 has remained unchanged to this day. Of course, I have never had it analysed and know of no other reference to that, but it is present on your Mindat page...


Cheers


Tim

30th Jan 2019 15:03 GMTUwe Kolitsch Manager

> As far as I know there is no XRD difference between torbernite and metatorbernite.


Of course, there is!

30th Jan 2019 15:24 GMTRichard Gunter Expert

Hi Uwe:


I was trying to figure out why the Dankoe Mine material would give a laumontite XRD trace. Sorry.

12th Sep 2019 21:29 BSTJeff Krueger

I've been wondering about the beautiful "laumontite" from thePine Creek Mine, Scheelite, Bishop Mining District, Inyo Co., California, USAWould it be more accurate to call it Laumontite var. Leonhartite? Many of the photos in the database allude to the possible
pseudomorph state.  Is laumontite ever stable in household humidity?  Is "laumontite" always a pseudomorph much like argentite and its lower temperature pseudomorph acanthite?

19th Sep 2019 17:26 BSTRichard Gunter Expert

Hi Jeff:

The Dankoe Mine material is a low-temperature phase that occurs with curly Native Silver and both cubic pseudomorphs of Acanthite after Argentite and spiky "primary" Acanthite. It does not appear that the Laumontite is pseudomorphed after another mineral as the small monoclinic crystals are transparent. I do not have detailed chemistry of the Laumontite to know if there are cations that stabilize the structure. In this case it appears the Laumontite crystallized directly and has not altered.

20th Sep 2019 00:47 BSTRonnie Van Dommelen Expert

01997640015689370435644.jpg
Eric,

In the past people in my area used a mixture of white glue and water.  You delicately apply to the specimen with a soft artists brush.  Several coats are possible and keep applying until just before it starts to pool between crystals.    It can yellow over time though.  A couple years ago we tried Elmers *clear* glue (and water).  At the very least, it seems to retain a more accurate luster - you cannot tell the glue has been applied and the specimens look good (IMO).  The yellowing problem may also go away.  I've had a specimen in my cabinet for a couple years now and it looks fine.

22nd Sep 2019 08:17 BSTJobe Giles

04443620015691363399958.jpg
Eric, I haven’t found a good method outside of the Elmer’s glue method to preserve mine. I tried mineral oil just out of curiosity and it altered the color but not the crumbling; I recommend against using it. Even with the glue mixture I still have dealt with crumbling or separation from the quartz crystals it covers. Though, once it separated from the quartz I used a small artists brush to brush epoxy onto the back and reaffixed it to the small Quartz crystal it was originally on (see above mounted on 1” block for scale).
 
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