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Author Topic: photomicrographs or other close-up pictures  (Read 76453 times)

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Offline GollyMrScience

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Re: photomicrographs or other close-up pictures
« Reply #40 on: February 03, 2010, 10:22:10 PM »
Do a quick check with a strong magnet. Magnetite weathering to limonite or hematite and maghemite are possibilities. As you say it could be a pseudomorph though I tend to head for the easy choices first.
What the heck - lets just keep mixin' stuff together till it blows up or smells REALLY bad!

Offline sluicedog

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Re: photomicrographs or other close-up pictures
« Reply #41 on: February 03, 2010, 10:55:55 PM »
finch68 and GollyMS.....wohhohhh slow down a bit for us poor minions.
I think we are all running as fast as we can to keep up  ^#!
This is all very interesting and NEW stuff...so if you would not mind, could you sorta slow down a bit ....so we can follow what you are saying.
This is very interestind stuff and I don't want to miss anything...

thanks guys
this is so cool

Offline finch68

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Re: photomicrographs or other close-up pictures
« Reply #42 on: February 04, 2010, 12:54:58 AM »
First to GMS - I separated my cons into 3 fractions with a super magnet (rare earth magnet).  The first fraction was material that was REALLY magnetic (jumped and inch or more to the magnet - mostly magnetite).  The second fraction was material that attached to the magnet when it was really close (mostly hematite, a few iron rich garnets, and some other slightly magnetic stuff).  The third fraction was the non-magnetic stuff.  The "limonite" was in the non-magnetic fraction.

Sluicedog - sorry - All minerals (rocks) weather or break down and change form when exposed to the atmosphere (wind, rain, freezing, thawing, lightning, etc), or subjected to chemical reactions or chemical changes due to exposure to alkali streams, acidic streams, heat, pressure, etc.  Even bacteria and other bugs chew away on certain types of rocks and break them down into smaller bits.  This is all weathering.  Very common weathering is simply the breakdown of rocks into smaller rocks due to mechanical things related to weather.  Pretty much all of the little rocks I am looking at under the microscope are the result of big rocks breaking down and getting beat up in the streams and rivers.

Another important point is that all minerals have specific "natural" forms that they like to show up in.  Salt crystals are cubes.  Garnets are 12 sided solids.  Fool's gold (pyrite) is usually cubic, quartz is 6 sided needles, and so on.

However, when some minerals weather chemically they can change into another mineral completely, but retain their original shape.  This is called "pseudomorphing".  A real good example of pseudomorphing is the formation of petrified wood.  The original wood (OK, not a mineral, but the process is the same) fell into a swamp and got buried with silt.  Over time the cellulose and lignin and whatever else wood is made of got replaced by rock minerals (silicates, etc) in a weathering process of sorts.  The end result is a silicate rock that looks like a tree, not like a silicate rock.

So back to my picture.  My thinking is that a crystal of pyrite that was originally a flat cube (I know that is not a proper term, but it conveys a picture) was exposed to chemical weathering and slowly converted into limonite, which is a closely related mineral.  Take my word for it that it is common for pyrite to weather into limonite.  However, limonite's normal crystal form when it crystallizes on its own is amorphous or shapeless - just a lump of shapeless rock.  However, when pyrite weathers into limonite it pseudomorphs into it.  In other words, when the weathering is complete and all the pyrite has turned into limonite, it still looks like pyrite in its structure.  It is like the petrified wood - you now have a limonite particle that looks like a pyrite particle.

Since this particle and others like it in my cons are completely non-magnetic when exposed to a rare earth magnet there is not very much chance that the crystal is a pseudomorph of magnetite as it would retain some of the natural magnetism.

I hope I didn't cloudy the water even more.

finch68

Offline GollyMrScience

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Re: photomicrographs or other close-up pictures
« Reply #43 on: February 04, 2010, 07:29:20 AM »
Yes agreed - there would likely be some reaction to a magnet if it was weathered magnetite or maghemite. Any idea how hard or competent the grains are? Or what a fresh face looks like if you can break one open? A pain to play with them at that size but a fun puzzle to solve. When I had a lab I could stabilize in resin and polish grains that size to get a good look. Could still be done but without all the toys to help it just adds to the hassle and after awhile a guy starts wondering how curious he is.
What the heck - lets just keep mixin' stuff together till it blows up or smells REALLY bad!

Offline finch68

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Re: photomicrographs or other close-up pictures
« Reply #44 on: February 04, 2010, 12:25:04 PM »
Thanks GMS for the comments.  I plan to make a few "thin sections" manually at home to look at fresh faces.  Won't be too difficult.  Of course they won't be true thin sections, but they might help with id of some minerals.

Before I get the "--wohhohhh slow down a bit" again, to make my sort-of thin sections i will use quick drying epoxy to glue a bunch of small particles to a glass slide.  Then I will sand down the particles using emery cloth (the hardest sandpaper I can find) until I have removed all of the original surfaces and exposed the interior of the particles.  I will examine the slide frequently under the microscope during this process to make sure I don't sand all the good stuff away.  This will let me see unweathered surfaces and might give a better idea of colour, hardness, crystal form and so on.

For those wondering why I would go to all this trouble - the "who cares" folk; there are a few reasons I do this.

1.  I want to see if there are any other "goodies" in my gravel.  It is easy to see visible gold, but it is not so easy to see platinum or platinum group minerals by eye alone.  It would similarly be difficult to id diamond, or ruby or some other precious and semi-precious stones.  If I can find little ones of any "goodies" under the microscope it might prompt me to look for bigger ones on my claim.  Also I want to look for micro-gold that is too small to see with the eye to tell me if there is any possibility of chemical (not merrcury  <~ShOcK~>) recovery of the tailings from gravity separation.

2.  I want to know if there are any "baddies" in the gravel.  We all saw the microscope pictures of very, very tiny mercury that willthedancer posted a couple of days ago.  I want to know if there is anything in my gravel that could harm me or those around me, so microscope examination can tell me.

3.  Unknown minerals can be either "goodies" or "baddies" or worthless/harmless, so I like to identify as many of the minerals in my samples as possible.  You never know when you might find something that is a potential money-maker.

4.  The more I know about what is in my gravel the better equipped I am to apply the most effective recovery methods (both physical and chemical) for the good stuff i want to keep.

5.  I have been a researcher all my life and I love doing it and it gives me great pleasure to share what I learn with others a long as they have an interest.  This should probably be the number 1 reason in my list.  I will always be happy to share the science behind my pictures/research if people ask questions.

I'll keep posting as long as people have any interest.

finch68

Offline tomcat

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Re: photomicrographs or other close-up pictures
« Reply #45 on: February 04, 2010, 12:47:49 PM »
finch68,
You can purchase Diamond sharpening stones from Lee Valley Tools (go online) if you run across harder Minerals or Gems than your sandpaper can cut plus they are on a steel substrate so it might give you a more controlled cut.

Offline finch68

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Re: photomicrographs or other close-up pictures
« Reply #46 on: February 04, 2010, 10:03:35 PM »
Thought maybe I'd change gear a bit and post some other interesting gold related stuff.  We've all heard about mossing and the ability of moss to collect gold, but how many have really looked at moss?  Here in BC riparian moss is protected, so it is not legal to go mining the stuff by destroying it.  In other words, you can't go and rip all the moss off the rocks to look for gold.  However, sampling a little bit no bigger than your thumb for research purposes might pass inspection.

Here are some pictures of moss from somewhere south of Yale from a sample smaller than my thumb.
This is a bit of skinny, young moss.

This is a sparsely leaved frond with a bit of sand clinging to it.

This is a closer view of an older mature frond - note the overlapping, shingle like leaves.

Another view showing how find sand loves to cling to the moss fronds.

This is the "flower" end of a moss frond - the part that waves around in the air.

This shows how fine sand loves to collect in the moss.

This is a closer view.  You can see the black sand among the blond sand.

And, believe it or not, I actually managed to find a very tiny gold flake clinging to some moss.


Hope you find these interesting.

finch68




Offline GPEX admin

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Re: photomicrographs or other close-up pictures
« Reply #47 on: February 05, 2010, 04:04:51 AM »
Morning Mr. finch

In commenting on your post, I must highly commend you on your originality and inquisitive insight.  Though once in a blue moon my mind would venture the thought of examining the texture of moss, as you have, it was just one of those things I never did get around to.  And your research does not cease to amaze me.  A most excellent job and excellent plates.  So interesting it is, one can easily see why Mother Nature’s ability to trap the fine to super-fine stuff, and her methods for doing so, far exceeds anything that man has so far devised or could hope to duplicate.  Such only stands to demonstrate a whole new standard for those who strive to perfect the ultimate sluice insert (matting).   

In regard to your research and its benefit to the placer miner, you stand amongst the leaders in the industry.  {-applause-}
Somebody said that it couldn't be done
But he with a chuckle replied
That maybe it couldn't but he wouldn't be one
Who'd say so until he had tried.

Offline willthedancer

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Re: photomicrographs or other close-up pictures
« Reply #48 on: February 05, 2010, 07:12:43 AM »
Yes-- what Larry said!
Naps are wasted on toddlers, only an adult can appreciate them. Looking for mine now.

Offline GollyMrScience

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Re: photomicrographs or other close-up pictures
« Reply #49 on: February 05, 2010, 09:42:05 AM »
One thing to keep in mind is that the moss has no efficiency expectations. It just is.
For every little flake saved it could have lost thousands but mom nature is patient. Where we have a few hours in an afternoon she has 24/7. No capital costs or operating costs to consider and even a marginally efficient system under those conditions will save enough gold to be anomalous (eventually). The bedrock crevices that we so like to clean out are not that efficient (by sluicebox standards) but they have been there collecting a bit of gold from all the gold that moved downstream and held onto it over many years. Eventually there is enough gold in there to get our hearts racing. In another way of putting it. You could use a sluice that saves 90% of the gold that you put in the top. You use it for a few hours and get that 90% to brag about. A bedrock crevice might only have a 0.01% recovery, or less, efficency but it applies that every day, all day, year after year after year.
By virtue of where moss can grow and the energies that are applied to it and the material that flows over it the recovery curve will be biased towards the fine gold end. It is no wonder that moss can be such a bonanza of fine gold given that it sits there year after year - flood after flood - recovering even minor percentages of the available gold will eventually add up to lots. On a shovelful by shovelful of paydirt efficiency basis a sluice will outperform moss (in my opinion) but that moss never gets tired and does not give a hoot how much gold per shovelful it is catching or how much it is costing to do so.
What the heck - lets just keep mixin' stuff together till it blows up or smells REALLY bad!

 


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