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Rei
Joined: 09 Apr 2014
Posts: 228
Location: Höfuðborgarsvæði
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Posted: May 07, 2014 17:14 Post subject: Crystal finds |
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So I've been having good luck on the chalcedony and especially crystal (primarily calcite) fronts of late. On a recent walk through my land I stumbled across an area whose rocks looked different - I was struck by the high olivine concentration mixed with high iron concentrations, and in some places streaks of white, as well as little amygdules and shiny flecks. Following a hunch, I checked the slope above there... and wow, it was a trove
Later, on a different slope I found a bunch of botryoidal specimens.
I assume most of this is calcite (because I know there's calcite in the area), but I haven't yet done a vinegar test. What I'm relly curious about however is the "hairy" / asbestiform structures which seem to blend into the crystals. Anyone have any clue what they could be?
All of this is rather dirty - it's straight from the ground, after all - but when my Iron Out comes after a couple months I'll give them a nice bath. :) The likelihood that they're calcite-bearing prohibits the use of acid.
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Olivine and iron-rich specimen Hvalfjörður, Iceland |
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Olivine and iron-rich specimen Hvalfjörður, Iceland |
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Part of the set that led me uphill Hvalfjörður, Iceland |
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Tiny embedded crystals Hvalfjörður, Iceland |
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Calcite embedded Hvalfjörður, Iceland |
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Calcite(?) druse Hvalfjörður, Iceland |
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Calcite(?) druse Hvalfjörður, Iceland |
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Calcite(?) druse Hvalfjörður, Iceland |
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Calcite(?) druse Hvalfjörður, Iceland |
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Calcite(?) and druse Hvalfjörður, Iceland |
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Calcite(?) and druse with asbestiform structures Hvalfjörður, Iceland |
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Calcite(?) and druse with asbestiform structures Hvalfjörður, Iceland |
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Calcite(?) Hvalfjörður, Iceland Not much to see here now, but I can see lots of crystals beneath the "gunk" - I think a nice soak in Iron Out will turn this into a good specimen. :) |
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Calcite(?) Hvalfjörður, Iceland |
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Calcite(?) with some sort of black mineral Hvalfjörður, Iceland |
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Rei
Joined: 09 Apr 2014
Posts: 228
Location: Höfuðborgarsvæði
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Posted: May 07, 2014 17:28 Post subject: Re: Crystal finds |
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A few more pics.
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Various pieces of botryoidal chalcedony Hvalfjörður, Iceland |
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Botryoidal chalcedony Hvalfjörður, Iceland |
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Botryoidal chalcedony Hvalfjörður, Iceland |
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Botryoidal chalcedony Hvalfjörður, Iceland |
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Miscellaneous calcite(?) Hvalfjörður, Iceland |
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dironot
Joined: 04 Mar 2014
Posts: 9
Location: Lompoc, California
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Posted: May 07, 2014 17:35 Post subject: Re: Crystal finds |
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Great finds! Please post some photos of the specimens after cleaning. I am also VERY interested in seeing pictures of the hillside/area features you are describing.
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Michael Shaw
Site Admin
Joined: 30 Apr 2008
Posts: 2069
Location: Oklahoma
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Posted: May 07, 2014 18:36 Post subject: Re: Crystal finds |
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Hi Rei,
You should check the hardness of your "botryoidal calcite." It looks more like chalcedony to me. This simple test will tell you quickly what you have.
Michael
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Rei
Joined: 09 Apr 2014
Posts: 228
Location: Höfuðborgarsvæði
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Posted: May 07, 2014 20:05 Post subject: Re: Crystal finds |
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crosstimber wrote: | Hi Rei,
You should check the hardness of your "botryoidal calcite." It looks more like chalcedony to me. This simple test will tell you quickly what you have.
Michael |
Whoa, you're right, it's harder than steel - can't be calcite!
Well, that'll make it easier to clean. :)
What about the fibrous stuff? Someone somewhere else mentioned that it could be a zeolite - does that sound plausible?
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Jordi Fabre
Overall coordinator of the Forum
Joined: 07 Aug 2006
Posts: 4896
Location: Barcelona
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Posted: May 08, 2014 01:34 Post subject: Re: Crystal finds |
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crosstimber wrote: | What about the fibrous stuff? Someone somewhere else mentioned that it could be a zeolite - does that sound plausible? |
Yes, https://www.mineral-forum.com/message-board/files/thumbs/t_s1390015_203.jpg looks like Stilbite or Barrerite.
You can check to see if it fizzes in HCl (5-10 %), if no fizzing, then check after long term immersion (1-2 day in HCl 5-10 %). If you get a kind of jelly-like substance, then you could have a zeolite, probably Stilbite or Barrerite
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Mike Wood
Joined: 16 Dec 2010
Posts: 456
Location: Northern England
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Posted: May 09, 2014 12:53 Post subject: Re: Crystal finds |
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Congratulations Rei, it looks like you have found some useful zeolites! Well, stilbite is good anyway. Nice crystals! They may only need washing in water to get the mud off.
The 'hairy' stuff is probably mesolite (one of the most common 'hairy zeolites) and if it isn't found clean, it is almost uncleanable. Very nice botryoidal chalcedony!
Was wondering if the first picture (with the greenish botryoids) might be prehnite, but it could still be chalcedony.
Nice one :-)
Mike
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Rei
Joined: 09 Apr 2014
Posts: 228
Location: Höfuðborgarsvæði
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Posted: May 10, 2014 02:58 Post subject: Re: Crystal finds |
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Thanks!
Not sure how to run any further tests without damaging them (aka, wouldn't really want to *dissolve* my zeolites by dunking them in HCl just to prove, yep, they were zeolites! ;) Hmm, maybe I could try to break off just one or two crystals and put them in a tiny container or on a microscope slide), but it's nice to have a good idea regardless. :)
Thanks for the mesolite tip. I found a document that says that mesolite doesn't clean well in anything water-based, as the fibers tend to clump up afterwards (like wet hair), and recommends (among other things) alcohol. So I'll give that a try.
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margaretB
Joined: 09 Jun 2014
Posts: 3
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Posted: Jun 09, 2014 02:24 Post subject: Re: Crystal finds |
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Thanks for the information. It was really a great thing to find science. As this crystal was formed and were beautiful.
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Rei
Joined: 09 Apr 2014
Posts: 228
Location: Höfuðborgarsvæði
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Posted: Jun 10, 2014 21:48 Post subject: Re: Crystal finds |
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Time for an update to this thread
Found a couple more zeolites while climbing waterfalls on the Fossá, a place I'd not been before. Guess that changes my "you don't find anything neat at waterfalls" atttitude ;) Like before, they were in eroding "mud". These aren't as impressive as the previous finds, however, so I haven't photographed them.
I did some additional investigations into the previous sample. First, I tested for reactivity with HCl.
* I could hear and kind of see a reaction with the druse, but it wasn't very fast.
* I don't think I heard a reaction with the fibrous material or its substrate
I then broke off a tiny crystal or two from the druse and a tiny chunk of the fibrous material and added them to a plastic container filled with a bit of 30% HCl. Again, I noticed an immediate reaction with the drusy crystals, but nothing obvious with the fibrous material - although there could have been something slow. The next time I checked back, the HCl had turned bright urine-yellow, a pretty impressive color change I'd say given that the HCl outmassed the crystals by 2-3 orders of magnitude. I don't know what material changed the color, but I'm guessing the druse. I left it in there for 1-2 weeks just to be sure any action was done. I was surprised that both minerals were still visibly present, though the drusy material looked smaller. I did some tests (below) pressing on them with a nail. The fibrous material was still quite firm and did not damage, but the drusy material shattered into little crystals with very little force. Nonetheless, they were still solid.
I diluted the HCl to irrelevance and placed both on a microscope slide. The drusy material held together by water surface tension and was hard to separate, but I managed to separate it enough to view. You can see a photograph below - there's both cracked platy crystals and small crystalline fibrous bundles. The bulk fibrous material that had little visible reaction with the acid was too thick to photograph via transmission microscopy, and in my attempt to do reflection microscopy, I accidentally shattered my only really bright light bulb in the house :Þ
Thoughts?
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HCl with zeolite samples Hvalfjörður, Iceland |
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HCl with zeolite samples Hvalfjörður, Iceland |
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HCl with zeolite samples Hvalfjörður, Iceland |
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HCl with zeolite samples Hvalfjörður, Iceland Lightly pressing the druse with a nail (breaks apart) |
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HCl with zeolite samples Hvalfjörður, Iceland Lightly pressing the fibrous material with a nail (no respsonse) |
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Zeolite samples after HCl exposure, mounted on a slide Hvalfjörður, Iceland |
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Microscopy of drusy zeolite sample after HCl exposure Hvalfjörður, Iceland |
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Mike Wood
Joined: 16 Dec 2010
Posts: 456
Location: Northern England
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Posted: Jun 11, 2014 15:45 Post subject: Re: Crystal finds |
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Hello Rei, thanks for the update. I can't tell you anything different from what I said earlier - I still think the platy crystals are stilbite (or barrerite, like Jordi said) and the fibrous material could be 'mesolite'. The discolouration of the hydrochloric acid is most likely due to iron leaching from the tiny bit of dark material from the edge of the druse, forming iron (II) chloride.
Mike
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Rei
Joined: 09 Apr 2014
Posts: 228
Location: Höfuðborgarsvæði
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Posted: Jun 11, 2014 17:00 Post subject: Re: Crystal finds |
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Thanks a bunch, Mike :)
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