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The snows are melting in the mountains... time for a zeolite hunt!
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Rei




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PostPosted: Apr 15, 2015 20:31    Post subject: The snows are melting in the mountains... time for a zeolite hunt!  

This winter's been horrible, one of the worst on record. There've been few times where's been more than three days between storm warnings. The biggest hit my land with 130 mile per hour winds, ripping down 2/3rds of my windbreak and flipping my storage crate over (among the damage, about 20 large windows totally shattered). Just a terrible, terrible winter.

But today was lovely and the snow has begun to melt from the mountains... and so I got my first real chance to go rock hunting again. And of course I wasn't going to miss that! I decided to explore a place where I previously found zeolites to see what I could find.

But, some pictures of the trip and the local geology. :)



17162227445_8d22894b7c_o.jpg
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Note the horizontal lines in the distance; these are dikes of resistant rock formed by magma intrusion at some point in the past few million years.
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Closeup of the dikes
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They're hard to see in the photo (they were easy to see in real life), but I started spotting these curious white crisscrossing lines in the riverbed as I approached on the ridge above.
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They're even harder to see here, but they precede each of the horizontal rapids.
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One of them just under the water.
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This one seems to be the key clue - it looks to me like some sort of hydrothermal infill into cracks, maybe chert?
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Columnar basalt earlier in the hike
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Lots of small caves on the opposite site.
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16542089463_9ddb652c5a_o.jpg
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Lots of high-iron deposits and even more high-sulfur deposits, sometimes in the same place. Maybe that means I should be hunting for pyrite?
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Bright mineralization on the other side of the river. No clue what it is.
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The river cobbles were all brightly colored cobbles (they looked even brighter colored in person). I always find this a good sign.
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17162144035_b52c52d216_o.jpg
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Strange type of breccia that was common in a small region. Any clue what's cementing it together? Looks almost like limonite, does limonite form breccias?
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Interesting mix of basalt, jasper, and zeolites, The bedrock below seems sulfur-rich and brittle.
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16975982309_b0faf12f44_o.jpg
 Description:
Zeolite vein
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Rei




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PostPosted: Apr 15, 2015 21:10    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

Okay, now for the finds. I haven't had a chance to do tests yet, but I'm guessing stilbite? Maybe for all of them? They'll be sort of hard to test but I'll do my best when I've got a chance.


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Still trying to find a good way to clean them.
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This green stuff confuses me. If I saw it on any other rock I'd assume that it's some sort of tiny lichen. So here I presume the same. But it always seems to grow on the black stuff. So is the black stuff also lichen? But in other specimens you'll see, it really looks more like mineralization. Is the black just a lichen-friendly substrate? Is some black minieralization and other lichen? I really don't know how to interpret the green and black.
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Are all of these really the same zeolite? Is this actually stilbite? Can't imagine how I'd test such tiny crystals.
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s1480017.jpg



s1480018.jpg
 Description:
I named this one "kongurinn" (the king) because it has the largest free crystals I've encountered in the location yet.

There's more in the same place I didn't have time to get to that may be even better.
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It's hard to photograph, but there's some sort of weird side mineral coming perpendicularly out of some of the crystals (no, it's not mud, it's quite solid and firmly attached, and looks like crystals)
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s1480022.jpg
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Another attempt to image them.
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Holding it for size
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PostPosted: Apr 15, 2015 21:55    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

A few more pics...


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I have to say, even though I suspect that that green is lichen, it's still pretty ;)
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There's something else growing inside... interesting. Don't know if it's the same thing.
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PostPosted: Apr 15, 2015 21:57    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

So anyway, that's it for this trip. Any answers, tips, or general thoughts on the above? :)
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PostPosted: Apr 16, 2015 00:19    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

Great post Rei. Some of that territory looks as though it just cooled off. The image of the colored river cobbles is wonderful.
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PostPosted: Apr 16, 2015 07:00    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

The colors were even more impressive in person. The purple is particularly striking.

Haha, well, from a geological perspective it's really young ;) The whole area only started forming a little over 3 million years ago. The last eruption in the region was about 100kya, although there may have been intrusions since then - but the volcano is believed to be extinct (almost everything here is a volcano ;) ). Glaciers ripped out the U-shaped valley during the various ice ages, and the river has carved a pretty impressive canyon through its bottom, so one can access the older rocks.

There's of course always been - and still are - hydrothermal fluids acting on the rock; typical geothermal wells today in the region are usually between a couple hundred and a thousand meters deep. So there's of course ample possibility of not only subterranean modification of rocks, but also historic features (hot springs, fumaroles, etc) that have since gone extinct.

Need to stop this post early, my parrot is on the floor trying to eat my newfound zeolites. :Ů
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PostPosted: Apr 16, 2015 08:17    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

Rei wrote:
...I haven't had a chance to do tests yet, but I'm guessing stilbite? Maybe for all of them? They'll be sort of hard to test but I'll do my best when I've got a chance.

Probably almost everything is Stilbite-Ca with maybe some Calcite like http://www.mineral-forum.com/message-board/download.php?id=58617 (easy to detect with dilute HCl) but if you have the chance maybe it could be a good idea to try to order an analysis of them. Sometimes these Zeolites looking like Stilbite could be Barrerite.
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PostPosted: Apr 16, 2015 08:48    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

I've never ordered a test before, how would one go about finding a company to do it? Would I have to send a sample internationally?
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PostPosted: Apr 16, 2015 08:52    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

Rei wrote:
I've never ordered a test before, how would one go about finding a company to do it? Would I have to send a sample internationally?

You will get a PM soon, please check it.
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PostPosted: Apr 16, 2015 08:56    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

Thanks - I'll check for the PM :). Also, just did a hot vingear test on the flaky interior growth of *52/*53, and got significant bubbling (I did a control water test to be sure), so that secondary growth does indeed appear to be calcite.

I love living in a place where one can find such minerals just sitting on the surface near, and sometimes on, my land, right outside of the city where 2/3rds of the population lives, in a country bigger than Ireland and Kentucky.

Makes one wonder what's underground and what's further afield. :)
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PostPosted: Apr 20, 2015 17:04    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

Great post Rei and thanks for sharing it with us. Nice to see the land again, re-emerging from the winter snow!

I'll have a go at some of the questions:-
The green blobs on the black stuff is all the same lichen, just the black part is previous growth, maybe last years.
Most of your specimens collected look like Stilbite, whether Ca, Na, or K - rich is only detectable by lab work. K - rich stilbite (Barrerrite, as Jordi stated above) is the rarest form by a long way. The crystals look large and well-formed, and quite 'fresh', meaning transparent. You could try a water-spray, or clean them under cool running water and use an artist's paintbrush to dislodge the dirt particles. Bleach might be necessary to remove any algae (lichen).
It would be worth your while to dig around in the area where you found these large stilbites, they look pretty good and there will likely be large geodes, probably formed in the same lava flow at the same horizon (layer) for a limited extent.

The small spiky mud-covered crystals around the edges of the stilbite specimen is likely to be a zeolite mineral, such as mesolite (or natrolite or scolecite), or laumontite.

The small sparkly ball-like aggregates of crystals in the smaller cavity look rather like prehnite (not a true zeolite but often with) but could also be quartz... not too sure.

The pale-coloured dykes could be an acidic magma, similar to rhyolite or pitchstone.
The purple rock next to the big dyke is likely to be enriched in iron, probably from hydrothermal solutions which are vigorous in Iceland, like you say...
The green coloured rocks under the purple coloured rocks look also iron-rich, but in the 'reduced' state chemically speaking (Fe2+, rather than Fe3+ for the 'oxidised' iron). There may be a chance of finding pyrite crystals in the green areas...

I hope you get the chance to get out exploring and collecting more this Summer, the land is looking good, thanks again for the photo's.

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PostPosted: Apr 20, 2015 18:29    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

Wow, thanks for all of the replies Mike!

I'm going to send several of these, plus some previously collected specimens, to Geo Spectra for analysis. I'd love to have a better idea of what I'm looking at and what I'm finding in each area :)

Okay, so it looks like all of the black is lichen, growing into the cracks between the crystals? Okay, then I'll probably remove it from the nicer specimens but leave it on the poorer quality specimens, as it has a sort of neat character to itself, with those dendritic growths.

Do any of these zeolites degrade in a manner that I should know about? I know, for example, that pyrite degrades (oxidizes) after being collected if not treated and/or stored properly.

Interesting if the pale parallel streaks are rhyolite dikes or similar (I'll check them out on another hike later this year I'll try to get over to them). Basalt is of course more common here but rhyolite is present, there's one rhyolite peak I know of about 13 kilometers away. Makes me wonder if they're from the same eruption. :) I also have some rhyolite in the glacial till on certain parts of my land which I always assume came from the peak, but perhaps it came from a dike much closer. Interesting - definitely warrants a closer look :)

Your comment about the green rock just made something click for me. Some of the chalcedony veins on my land have green in them, particularly one further to the west which yields this beautiful glassy green chalcedony. I had long assumed that it was copper that gave it the green, but iron here is much more common and I forgot that Fe2+ can give things a green color. The vein is only about 100 meters from a spot where there's bright red clay over "rotten" rock that crumbles easily - which especially given how rare clay is here, strongly suggests to me that it used to be the site of some acidic water flows. Something tells me I should take the time to do some more digging in the area :)

The same area also has some calcite veins - which obviously were either untouched or deposited later if there were acidic water - and some interesting quartz specimens, such as this sizeable weirdo (so far I've only rinsed it, no additional cleaning):

http://www.flickr.com/photos/54125007@N08/16594945734/
http://www.flickr.com/photos/54125007@N08/17009942577/
http://www.flickr.com/photos/54125007@N08/17009938697/
http://www.flickr.com/photos/54125007@N08/16594929664/
http://www.flickr.com/photos/54125007@N08/16594942024/
(links normalized by FMF)
Sure looks like it formed inside some other minerals that have since disappeared, though I haven't a clue as to what!

As for the place where I was finding the zeolites, I'd have to apply for permission to dig there, it's public land. But no need to dig at this point when one can still find these sort of specimens just sitting loose on the surface! I've only walked a rather small portion of the productive area, and could see sizeable pieces at areas that I decided not to take the time to get to (45░ talus slope, it takes time to move up and down them). But yeah, I'm sure there's some gorgeous beauties just sitting underground there.

I probably won't hit that exact area again in my next several hikes - I want to explore some of the side canyons (there's tons) to see what else the mountain holds, and maybe hit the other side of the main canyon opposite the big zeolite area to see if the deposit extends over there too. There's just so much to see, I've barely gotten more than two kilometers from the main road in the country, 15 kilometers from the center of the city where 2/3rds of the population lives, haha ;) The zeolites are only 1km from the main road (by contrast, the valley that I've been hiking in is 7 1/2 kilometers long and up to 4 kilometers wide). Oh, and erosion (which is a big problem here) regularly exposes brand new stuff (by picking up beautiful stuff you're actually saving them, these pieces would probably end up crashing down into the river and be destroyed at some point in the next couple decades if just left there). Iceland really is a great place for rockhounds. :)

Anyway, thanks for the info! :)
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PostPosted: Apr 22, 2015 12:51    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

Hi Rei, you're welcome, it would be interesting to see the lab results :)
The green and black lichen should be removable after soaking in a cheap chlorine bleach solution, but might still require gentle scraping to shift it. The minerals should be fine with bleach; they are in my experience, only thing is it takes a fair bit of rinsing and soaking in clean water to get rid of the smell!

A few zeolite minerals can degrade and fall apart due to dehydration, laumontite is most famous for this. Chabazite seems particularly prone to internal crazing, when left in direct sunlight after being exposed for the first time, even for just a few minutes. As a rule I place collected specimens in the shade immediately after extraction, unless it's very cloudy of course. This may be an effect of heating causing crazing, but I'm not sure. Stilbite should be ok, but will eventually go white and opaque if left in the sun.

The red clay on your land could be the top of an olivine-basalt lava flow that has completely decomposed, due to hydrothermal action. I think this is how bauxite is formed. There used to be bauxite (aluminium ore) mines in Northern Ireland, where there is of course a lot of basalt lava flows from the Tertiary period.

One more thing, the photo links don't work for me, without signing up for ya-how, that is ;)

Happy hunting!

Cheers, Mike

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PostPosted: Apr 22, 2015 17:51    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

Wow, thanks for the warning about light - I had no idea! That's important to know! Should I do anything with any of my samples to prevent dehydration?

I'll just insert the above pics into this post. :)

I went out today to a beach where I heard one can find high quality spherulites today, as I don't yet have any in my collection. Didn't find any, but but I found some more pretty zeolites and some lovely prehnite (presumably) druse. Only one small patch of ground was productive, but still, I wasn't expecting anything like that, the ocean is a pretty destructive beast.

Seems like everywhere you walk off the path here and look down you can find something neat ;) Can't wait to try out this area, the geology should be totally different than my immediate vicinity:

http://www.geothermal.is/32-tjarnarhnjukshraun-vid-olfusvatnsa-xenolithes
(link normalized by FMF)

"The rock type is picrite crowded with olivine phenocrysts, which are enriched in the lowest part of the pillows from crystal settling. Crystal settling of plagioclase xenocrysts (bytownite) can also be observed in a porphyritic pillow lava in the same gorge north and south of the MŠlifell unit. The lava is rich in gabbroic xenoliths, which are best seen in the section along Ílfusvatnsß. Their mineralogy varies depending on which primary phase predominates, but most common are feldspar- and olivine-rich ones."



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Iceland
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The quartz "weirdo" from my land. No significantl cleaning done yet.
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Note the strange indentations all over it - is this a pseudomorph or something?
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PostPosted: Apr 22, 2015 18:40    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

Today's finds (honestly, I wasn't even planning to go on a hike today! And then I was only planning to look for spherulites!.... but, but.... ;) )


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 Locality:
Iceland
 Description:
Found two pieces like this: sizeable, on a thick substrate, and covered in thin, intercrossed crystals. They were in their own location and while the crystals may be ones I've found thusfar, the form of the sample is not.
 Viewed:  13819 Time(s)

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 Description:
Holding it for size
 Viewed:  13855 Time(s)

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 Description:
The substrate is somewhat translucent and shifts in hues.
 Viewed:  13850 Time(s)

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 Description:
Very pretty piece right by the seashore (in an area surely hit by storm waves). It unfortunately broke in two in my pocket, it must have been nearly broken already.
 Viewed:  13834 Time(s)

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 Description:
 Viewed:  13827 Time(s)

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 Description:
Size
 Viewed:  13830 Time(s)

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 Description:
 Viewed:  13833 Time(s)

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 Description:
 Viewed:  13829 Time(s)

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 Description:
 Viewed:  13833 Time(s)

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 Viewed:  13822 Time(s)

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 Description:
 Viewed:  13828 Time(s)

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 Description:
 Viewed:  13838 Time(s)

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Rei




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PostPosted: Apr 22, 2015 18:43    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

Two more :)


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 Description:
 Viewed:  13818 Time(s)

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s1490026.jpg
 Description:
 Viewed:  13837 Time(s)

s1490026.jpg


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Mike Wood




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PostPosted: Apr 23, 2015 14:52    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

I would think the climate in Iceland would be humid enough most of the time, to prevent dehydration of most zeolite minerals, except for laumontite which really needs to be kept in a permanantly wet environment (I keep mine in a cheap plastic see-through box with a lid, with water in it). Just keep them out of sunlight and away from direct heat and they should be fine :)

The weird quartz specimen with the holes in it looks like chalcedony, with calcite (probably) formally occupying the holes... I think I can see some thing resembling calcite in the last photo of that post.

The beach you went to looks promising if your last specimens were easily found! The first specimen with the interlocking thin platy crystals is stilbite, I have seen much of the same type of material on the Isle of Skye. The other specimens are also mostly stilbite but in a very different form! They look good and fresh and are good specimens; particularly the one with the chabazite crystals on. I know I'm being presumptious here but those clear pseudo-rhombohedral crystals look exactly like chabazite to me! Similar to rhombohedral calcite crystals of course; the acid test will decide!
Those 'cauliflower' stilbites are really neat. One crystal looks like it is forming a 'bowtie' shape, ie a double-terminated crystal. Good stuff.
Stilbite occurs in many different forms, but I reckon the two examples you have found are about the two extremes.
Of course, the crystals might be a bit worn by surf action, and might dry out a bit white. If there are any boulders around on the beach it would be worth breaking them up with lumphammer and chisels to see if there are any large fresh geodes inside - there will be, because that would be the source of your finds.

It's right what you say about minerals getting destroyed, by not picking them up and preserving them. What's the point of leaving a good specimen lying on a rocky beach when it will very soon get reduced to dust by the timeless pounding of the waves? Should be allowed ;)

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PostPosted: Apr 23, 2015 18:56    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

Mike Wood wrote:
The weird quartz specimen with the holes in it looks like chalcedony, with calcite (probably) formally occupying the holes... I think I can see some thing resembling calcite in the last photo of that post.


You know, that makes sense. I've been very confused by that piece because it has such angular facets in most places like I'm used to from quartz, but curved in others (even botryoidal in places), and it has a foggy color I more often associate with chalcedony. My tests showed it had your standard SO2-tetrahedral forms . So all of those many flat faces are most likely from calcite. Interesting, because I've never found such large calcite crystals on my land! Abundant smaller crystals conjoined together, but nothing of quality, I wonder if there are still some nice big ones like that somewhere. Maybe I'll find time to dig one of the nearby veins later this year :)

Quote:
The beach you went to looks promising if your last specimens were easily found!


It was literally a "Okay, I'm not finding any spherulites over here on the sand, I'm just going to crawl up this ridge here and, oh hey, what is this my hand is touching?" moment ;)

I'd love to break some rocks but I always try to stay legal, so I'll need to see if I can dig up who, if anyone, owns the area. I believe it's public land, as there's a parking lot not far from the place, some simple footpaths, and an info sign about the birds that nest in the area - I think that's the main draw for most people, seeing the eider ducks and the like. But I'll need to enquire around.

Thanks for all of your great comments on the samples! I'll definitely be hunting some more later. But right now I'm still working on expanding my list of "known hunting grounds" ;) So far it's all been right near my land. Tomorrow I'm going to head out to a canyon about 45 minutes away where if I'm lucky I may find some nice loose olivine xenoliths and/or bytownite. It's not a very visited canyon (like most of the country, lol)... and I imagine the far, harder-to-get-to side is almost never traversed, though I'll try the near side first ;)
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PostPosted: Apr 24, 2015 18:17    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

I've just been looking at the last photo's again and realised I had forgotten about apophyllite - which can look like chabazite when it is in small pinacoidal crystals. Some of the pseudorhombohedral (almost cubic-looking) crystals in the photo's appear to have a slightly curved face, which is more indicative of apophyllite where the pinacoidal face is often concave to a slight degree.
Chabazite is always of regular form in my experience, with flat smooth faces all equally lustrous.
Apophyllite has a vitreous lustre on the sides (pyramidal faces) and very often a more 'pearly' lustre on the end face (pinacoid). There are very often cleavage planes parallel with the pinacoid face, right down the length of the crystal. It occurs in a large variety of forms (habits), it isn't classed as a true zeolite but it often occurs with them.

Hope your trip to the canyon is enjoyable!

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PostPosted: Apr 24, 2015 21:05    Post subject: Re: The snows are melting in the mountains... time for a zeolite hunt!  

Interesting. Well, I've got a package ready to send out for ID, so I guess we'll find out!
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