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 Post subject: A good day that turned out crap
PostPosted: Sun Sep 18, 2016 5:35 pm 
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Location: Central Queensland, Australia
Back down to the amethyst dig yesterday, I hit a patch of ground heavily replete with crystals. I ended up with about a third of a two-gallon bucket of crystals and pieces, a couple of crystals just a bit smaller than tennis balls.

I felt very satisfied as I drove home. But when I cleaned them up, satisfaction turned to disappointment - out of all that amethyst there was just a few small pieces that would yield faceting stones :( They were virtually all just rubbish, badly fractured and shattered.

I pinned my hopes on this piece.....

Image

....but when I put a few windows on it, it was just too badly fractured to facet. But the colour (not really evident in the photo) was so nice I thought I cab it instead. Started warming it up while I mucked around putting some wax on a stick. Then I hear a bang! Turned around - the bloody thing had exploded!! I found couple of small bits on the floor, the rest of it must be at the back of the benches somewhere.

So out of about six pounds of crystals I get virtually no usable material and the one bit that would have made a nice enough cab commits suicide when I try :) Some days are like that.

I'm wondering if the problem with these crystals might be their proximity to the surface? They are only about eight inches down - they would surely have been exposed to the heat of countless bushfires burning just over top of them.

I'm considering taking the demolition hammer down there to investigate the decomposing granite beneath - it's a bit hard with a crowbar and pick but the hammer should handle it easily. The best, cleanest crystals I've found have usually been in pockets and pipes extending down into the decomposing granite floor. Might was well investigate it while I'm on leave and have time to do so.

It would be nice if there actually turns out to be plenty of high-grade faceting and specimen material just a bit deeper down in pockets. Really, I think there are almost certainly seams and pockets all through the stuff down to significant depth - but is it worth digging down after them? That's what I want to know.


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 Post subject: Re: A good day that turned out crap
PostPosted: Wed Oct 05, 2016 12:51 pm 
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It's absolutely worth digging for!

Here in Ontario, Canada, we work solid billion-year old granite of the Canadian Shield for amethyst; a pick and bar have no impact whatsoever, it's all dynamite work.

It's hard to judge from the photo, but it does look like good tumbling material.

And remember that good sharp crystal specimens can be valuable and should not to be ignored.

As a mineral collector, I'd be most eager to put a week's work into that area at the drop of a hat.

I hope you go back, and let us know what you find!


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 Post subject: Re: A good day that turned out crap
PostPosted: Wed Oct 05, 2016 10:31 pm 
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Joined: Wed Sep 02, 2015 10:52 pm
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Location: Central Queensland, Australia
Oh I'll be back there don't worry, the prospectors blood in my veins won't let me quit :) - it sounds like you and I both agree that there's nothing quite like watching a millions year old crystal or gemstone tumble from the ground and knowing that you're the first human being who has ever laid eyes on it. Gives me a rush :D

Wow, blasting from solid granite - I must confess I've never mined using explosives :) My dad used to have a "powder monkey's" licence many years ago when he had a little gold mining claim before he got into sapphires, but they'd be almost impossible to get nowdays I'm guessing.

So how are your crystals distributed thoughout the rock? Mine are in thin, horizontal bands under the decomposed granite sand which sits on a hard floor of granite that has not yet fully decomposed. Sometimes you find a pocket that extends down into the hard floor and that pocket often contains better crystals. I'm assuming that these were veins and vugs in the granite when it was still solid. I guess it might be difficult to tell what the layout of things was after blasting has taken place ?:)

Do you find that the quality of the crystals can vary over short distances, with good ones seeming to be concentrated in small patches? That how mine seem to be.


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 Post subject: Re: A good day that turned out crap
PostPosted: Wed Oct 05, 2016 10:35 pm 
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Joined: Wed Sep 02, 2015 10:52 pm
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Location: Central Queensland, Australia
Quote:
As a mineral collector, I'd be most eager to put a week's work into that area at the drop of a hat.


If you ever end up making your way down here to Queensland, let me know and I'll take you on a digging tour of my local region if it coincides with my leave - there's amethyst and smoky, garnets, sapphires, zircons, labradorite, thundereggs and more :)


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 Post subject: Re: A good day that turned out crap
PostPosted: Sat Sep 23, 2017 4:45 pm 
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Joined: Sat Nov 05, 2016 11:29 am
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Lefty wrote:
I'm wondering if the problem with these crystals might be their proximity to the surface? They are only about eight inches down - they would surely have been exposed to the heat of countless bushfires burning just over top of them.


Lefty,

No, I don't think it's proximity to possible brush fires... The energy release there is pretty fast, and it would affect anything on the surface, but not more than a few inches below the surface.
Any rise in temperature would be very slow, thus the temperature change of the crystals would be slow, and thus there shouldn't be much thermal stress to them.
Likewise, the Emeralds found in the North of British Columbia are damaged down to 30 feet: No heat there, but there are freezing stresses due to the presence of water.
I suspect that the crystals are suffering the effects of weathering, but much slower than the surrounding rock.


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