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 Post subject: Beautiful Blue
PostPosted: Sun Aug 10, 2008 6:40 pm 
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The flying mammoth

It could have been a beautiful day. A clear blue sky, 15 degrees Celcius, crisp air and hardly any wind. The last generations of mammoths were roaming the area. Humans had been around for over 250.000 years but the recent climate change allowed them to travel up north further and for longer periods. The time is the Early Dryas (some 12900 years ago), the place what we now call the volcanic Eifel in Germany.
A young hunter had been stalking the herd for days now. Being part of the ritual to become a man he was sent out to kill a large animal. The group had been coming this far north for a few generations now and every summer the hunt had been good. Large herds of mammoths roamed the plains to the north and were frequently encountered in the new forests of northern mainland Europe. Since the temperatures had risen, according to the elders at camp some 10 generations ago, birch and pine forests had found their way to the north where before just steppe was found.
Today, after several days of patient stalking, a young mammoth had wandered off from his mum and was now happily grazing the grass some 30 meters away from the hunter. Quietly the hunter moved his spears to the front. The calf came closer and closer. Then, just when the young man wanted to jump up and go for the kill a loud rumbling sound came from the deepest of the earth. It started suddenly and died off after a few moments. The calf panicked and ran uphill back to the herd, away from the hunter. Not understanding why the spirits of the ancestors had prevented his kill with the strange sound the young man sat down on a large boulder that had been carried to that spot by the glaciers of the past.
Suddenly the sound returned, even louder this time, followed by a severe shaking of the earth. The hunter was thrown off the rock and ended up upside down in a dip behind the boulder. Then the blast came. An explosion 500 times the one above Hiroshima in 1945, the air was sucked out of his lungs and his eardrums were torn to bits. The last thing the man ever saw was the young mammoth flying by.
The Laacher See volcano had erupted.

Image
a nice insight into the magnitude of the inferno, the wall you're looking at is easily 50 meters high

Precious rubble

The initial blast of the Laacher See volcano eruption changed the appearance of the landscape immensely. The shockwave and earthquakes changed the relief of an area hundreds of kilometers around the centre of the volcano. The rubble that was ejected to a staggering 15 kilometers high caused thick deposits closer to the volcano. The inferno lasted for about 5 days. Magma and pyroclastic flows came racing down the sides of the volcano. Debris from the blasts rained down on earth. It is in these layers of debris and pyroclastic flows that a wonder of nature is found: Hauyne.

Image
a 0.65ct piece of rough, the biggest we found in two days

Hauyne is found most in the pyroclastic layers but occurs as well in the other deposits, even in the basalt that crystallized from the magma. Mining activities have been dated to pre roman days by archeologists. Pumice, basalt and other volcanic deposits being the sought after materials. Hauyne must have been found by these early diggers and when one sees a piece one knows that nobody would leave it where it is. A blue color unseen in any other stone makes it truly a collectors item. Looking through the spectroscope the cause of this awesome blue become apparent. A full absorption of the red to yellow is visible in the piece pictured above:
Image

If you ever acquire a cut stone I strongly discourage wearing it; the stuff is VERY brittle. Add to that a hardness of about 5 on Mohs’ scale and you have yourself a stone that will be scratched by 80 % of this planet’s dust and will fracture upon the slightest blow.
Nowadays collectors can step into the footsteps of several pumice miners to collect hauyne. A couple of quarries have opened up after WWII on the south-eastern side of the volcano. In the weekends the quarries aren’t worked and collectors enter the quarries in search of the beautiful blue. Since we consider ourselves to be collectors my better half and I went out searching for some hauyne of our own.
Experience learns us that local knowledge is the key to success for a newbie so we were glad to see that we weren’t the only ones there. And we hit the jackpot when it comes to local knowledge. We found in front of us a guy named Jozef who carries the nickname of ‘Hauynekönich’ (King of hauyne). He has been scraping the quarry floors for over 40 years and can be called the authority on German hauyne fossicking. The King found the biggest piece of hauyne that I (and he) knows of: 32 ct in the rough, it cut a whopping 10 ct or so. He further told me of some previous sales of cut stones in the 3-6 ct range going for about 10.000 euro’s per ct. Now that is precious rubble!

Image

a few stones the King had in his pocket, the big pear in the middle weighs 1.6 ct

Are you really surprised?

When stones start selling for 5 figure prices there is bound to be a treatment being found to increase ones income. In this case it isn’t the color that needs modifying. No, No, even the less saturated pieces are gorgeous. That said the darker colored pieces bring in the thickest dough so a little dying here and there may take place. Stones are often fractured and when the lapidary has mastered cutting such a piece blue dye could easily be squeezed in a fracture near the culet thus changing the color. But, this is just my suspicious mind working, no clues to dying have crossed my path yet.
The treatment I want to name here is that of stabilizing/fracture filling hauyne. Being a stone this brittle, rather soft and allergic to heat the beautiful blue is a real challenge to cutters. Many a possible large stone has ended up in pieces in the water tray of a disgruntled cutter. So treatment to the rescue! I found the guy that does it best and gave him a ring. Our conversation in a nutshell:
Me: Hello, my name is Tim Spauwen from Holland
He: Hello.
Me: I hear you can stabilize hauyne?
He: yes that’s correct
Me: How do you do that?
He: I’ve built a little vacuum-pressure chamber in which I place the stone and then create a vacuum to pull out all air and liquid that sits in the fractures. Then drop a bit of Loctite on it and increase the pressure, thus forcing the stuff to penetrate the fractures. After that I take out the stone and harden the Loctite with UV light.
Me: ok… any way of detecting that Loctite filling? Like different colored flashes under 40x?
He: No that is very difficult. Basically it’s chemical analysis that will reveal the filling, nothing else. I do tell all my customers that the stones I sell are filled.
Me: ok that’s very nice of you but do your customers the same when they sell their stones on?
He: that I don’t know.
Me: me neither, thank you for your time.

Loctite has an RI of 1.5 where hauyne has an RI that lays in between 1.496 and 1.510 so it would be hardly visible and chances are you get a clear refractometer reading when testing a filled stone. So for us gemmo’s with just the basic equipment this treatment is probably very hard to detect.

Image
hauyne rough, sizes 3mm to 7mm

If you ever go fossicking near mendig and find yourself a nice large cuttable piece that's imbedded in pumice DO NOT be smart and try to clear the pumice with hydrochloric acid. The hauyne turns into jelly upon contact to this acid...
Hard data:
http://www.mindat.org/min-1833.html
http://rruff.info/hauyne/display=default/R070121


Last edited by Tim on Sat Apr 25, 2009 11:20 am, edited 1 time in total.

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PostPosted: Sun Aug 10, 2008 9:14 pm 
What a fascinating piece of writing in how it connects the past to the present day. I was not familiar with the Laacher See eruption, but judging by the depth of deposits it was significant. If those 50m+ of tephra represent one event or several successive ones, that would have changed the face of the region. :shock: By contrast, the Mt. St. Helens eruption here was 0.004 of the magnitude.

And what a beautiful mineral to find in pyroclastics! I see there are deposits limited to Europe and E.US, which suggests a very specific magma chemistry. It appears there's no chance to find hauyne around Pacific Rim volcanoes. :(


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PostPosted: Mon Aug 11, 2008 3:59 am 
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WOW Tim :D
exceptional and VERY informative report!!
I'm impressed :shock:
BRAVISSIMO 8)
ciao
alberto

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PostPosted: Mon Aug 11, 2008 1:31 pm 
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Hi Spauwe ,

You're stories are the greatest to read , you start out giving a history lesson and bring us to what we love gemstones :wink:

very interesting :smt041 , did you get any nice specimens of hauyne ? pics ? besides that one :oops:

any idea when we'll start the chats again ? :smt090


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 Post subject: The flying mammoth
PostPosted: Tue Aug 12, 2008 2:37 pm 
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What a storyteller, you really make me proud :smt042
And a nice stone too, what if I cook you dinner and you bring me a small one....
good job son!


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PostPosted: Tue Aug 12, 2008 2:46 pm 
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sounds good! Steak and chips?

Thanks for the compliments all!


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PostPosted: Tue Aug 12, 2008 3:07 pm 
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so how hard was it to get to this place?? were there any special spots to dig?? did it cost to dig there?? How did you recover the stones from the ground and separate them from the dirt?

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PostPosted: Tue Aug 12, 2008 5:52 pm 
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Quote:
so how hard was it to get to this place??


very easy... check this out on Google earth:

50°23'29.54" N 7°16'28.34" E

the big lake to the north of the quarry is the crater of the Laacher See volcano. The road you see running from the west to the east (south of the quarry) is a major highway from Cologne to Koblenz. A car will get you to the gate of the quarry. During the weekends you simply walk in there...

Quote:
were there any special spots to dig?? did it cost to dig there??


at the moment the worker(s) aren't working the right layers. The whole quarry is more or less on it last legs I was told. "Back in the day...." you know the story...
Digging isn't the way for several reasons:
1. you would be digging in a vertical wall that is everything but stable. It is ash and debris and the whole thing is still very young geologically speaking so it hasn't compacted yet. Unless you have a death wish you shouldn't do it...
2. if you start digging there I think the party will be over very soon. The miners would put up fences and may throw in a couple of hungry Dobermans.
3. when covered in ash, a piece of hauyne will NOT be detectable amongst the gazillion other small pieces of rock out there.

Quote:
How did you recover the stones from the ground and separate them from the dirt?


funny you ask... I had this great idea about which I was convinced it would work: I would build a willoughby... A what? A will-it-be... The thing we use in Australia to separate sapphire from all other gravel.

A quick tutorial:
Image

one takes:
- a cement tub,
- a couple of jerry cans
- a parasol stand that you can drive into the earth
- a set of round sieves (one quarter inch, one about 2 mm) that fit in each other so you separate sizes,
- two pieces of 40mm sturdy pipe about 1.5 m long
- a trampoline spring
- a bit of 2mm thick aluminum band long enough to make a ring off in which the sieves will sit.
- 2, 1m lengths of 4 mm thick metal band &
- a dog (optional)
And join ‘m together to create something like in the picture below. (imageshack is giving me grief so no elaborate ‘how-to’. )

Image

You then get the wife to work and enjoy the sun (I wish… 8) )

Image

The whole idea is that you can create an up and down jigging movement of the filled sieves in water so the heaviest minerals end up centered in de bottom of the sieve. When you flip it over the goodies will be on top.
Hauyne’s SG is about 2.5 where pumice’s lies below that of water so in my dreams I was submerging a sieve full and just scooping all the crap of the surface, leaving a couple of pieces of hauyne in the sieve… Not all dreams come true though... I ended up with a sieve full basalt bits. A testpiece of hauyne made it to the second or third layer from the bottom so we pulled the pin on this technique and pointed our asses to the sky and noses to the ground. The good old specking technique proved to be more effective…

Image

the bits you want to find... (not my hand unfortunately)


Last edited by Tim on Wed Aug 13, 2008 3:50 pm, edited 2 times in total.

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PostPosted: Tue Aug 12, 2008 6:00 pm 
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NICE tutorial Tim :D

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PostPosted: Tue Aug 12, 2008 6:43 pm 
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wow, thanks, so you just walked up to the piles on the ground and started picking through it ??

Do those things fluoresce at all??

I don't know what it is about that color, but it makes me want to get a few... :)

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PostPosted: Wed Aug 13, 2008 2:16 am 
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Quote:
Do those things fluoresce at all??


LWUV ----> a slight chalky pink
SWUV------> no idea

that's the missing link in my gemlab, a good LW/SW UV light...


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PostPosted: Wed Aug 13, 2008 4:54 am 
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Spauwe wrote:
A car will get you to the gate of the quarry. During the weekends you simply walk in there...


What if I had a day to burn in Cologne between two meetings ? :? Any chance to see a little bit of something blue in the dirt in one afternoon? :roll:


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PostPosted: Mon Sep 01, 2008 4:38 am 
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Update on the filling detection: UV light may reveal the presence of a filler.


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PostPosted: Sun Sep 14, 2008 5:07 am 
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Wow Tim! That is a fantastic blue... that big fellow on the left of your hand. Its like those old cobolt blue medicine bottles... best blue around! If only I could find some to facet.

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PostPosted: Mon Sep 15, 2008 5:43 am 
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Hi Doug,

how is things out bush? Unfortunately that hand above is not mine. On the other hand, if my hands would look like that I would start too worry ;) They belong to a 60+ year old... But surely a nice hand of hauyne facet rough!!

I'll do my best to lay my baby skin hand on some decent size rough and will post it up for sale here in the classifieds. It'll require some very cautious cutting though... :-k


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