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NcSwampfox71

Quartz vein gold

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Around here we have lots of gold bearing quartz and my question is this... The quartz is a secondary enrichment for lack of a better term and the free milling gold was either formed in or brought in with the quartz. Where in the vein would the gold form? I guess I picture the gold "settling" to the bottom of the vein, my buddy thinks that in the liquid molten rock that the gold would "float" to the top of the vein like the hotter liquid in a lava lamp. Any educated guesses?

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gold forms out of quartz by crystalisation in fact all vien gold originaly formed by crystalisation. you'll normaly find gold in the thiner viens ~1 inch +-. were the super heated water moved the slowest alowing the gold to accumilate.

gold falls even when heated. so think of an underground river running through a large fissure. the disolved gold will consentrate in cracks were the water is moving the slowest. disolved gold is atomised gold, so you can imagin how slow the water must move. that's why gold often forms stuck to one side of the vien. and also why in the thin viens but "usualy" not thick ones. as the water moves slower through smaller fissures.

the rate at which the water cools determins the size that the crystals will form. fast cooling gives small crystals, slow cooling gives large ones.

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Ok I was picturing the quartz as a molten liquid like glass I guess, you are saying that the gold and quartz are formed as a precipitate from a water solution moving slowly under great heat and pressure through the fissures in the country rock. The whole reason I was asking was just what you mention that the gold can accumulate on one side of a vein. We started this discussion because my buddy and I were looking at an area that has a layer of cemented black sand and just below that a layer of quartz and dissolved bedrock its all full of modern trash but has allot of color in it. I picked up a quartz rock that was full of iron and magnetite. It was noticeably heavier than the other quartz so I brought it home. I do not currently have a mill but just in breaking the rock into a few smaller pieces i found a few flakes and a little piece of wire gold. I cannot wait to pulverize the rest of it. And quite a bit of the quartz material has similar mineralization. Pondering collecting the quartz that has the magnetite inclusions and investing in a detector to high grade it and crush it.

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Mostly quartz vein gold will be at the contact zone of the quartz and country rock, as Nuggetier mentioned the side of the vein, but it can also be within the quartz itself if the gold concentration is rich enough.

Skip

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Just a couple drawings for reference to where and how deposits were formed...

gold-diagram.gif

GoldDeposits.jpg

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Hey bill those are great images, thanks!

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Lots of good info thanks for all of it. I want to ask if the iron and other heavies collect along the contact surface also. I have found free milling gold in some vein material and do not as of yet have detector to high-grade the quartz with, and no rock crusher. Just wondering if I should grade the quartz by mineralizaton and play with hand crushing a few samples.. nothing too serious just for fun..

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in it's natural form and after it has been in an acid bath

You can see how the gold infiltrated the cracks and crevises

post-25522-0-95269400-1333407673_thumb.j

post-25522-0-73749400-1333407737_thumb.j

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awesome pic's Geojack, I have found several specimen's but never anything with more than a few small specks of gold. But I think I may be on the right track with this vein.

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in it's natural form and after it has been in an acid bath

You can see how the gold infiltrated the cracks and crevises

Geo,

The second picture, is that quartz? And is the gold as fragile as it looks? Tk's!

Rim

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Same rock in both pics, and yes, very fragile. Tears me up to watch it being processed as the handling of the piece breaks off small arms of the gold.

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I'm bringing back this old thread for another related question. I've always pried out the quartz vein and looked for gold trapped within the quartz. I've not had much luck. I know the contact spots are good places for gold to occur. A lot of veins I see are right up against a huge rock or fault, or between two visible faults on either side of the vein, but sometimes there's just one rock face. Usually the quartz is right up against the rock. I always assumed that was the contact zone and that the gold would be trapped in that quartz against the rock. So is it possible the gold would be in the tiny space between the actual quartz vein and the rock itself? Usually when I pry a piece of the vein off the rock face there is a little bit of discolored dust or material left on the rock. Is the contact zone the vein itself or the tiny space between the vein and the rock? Which one is the most likely spot to look?

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Chris,the gold doesn't always make where one thinks it would such as before or after a bend in the vein,a faulted spot, narrowing or widening etc.All veins that carry gold do not always have species or enrichments(pockets).Take your samples from different spots on the vein and follow the lead.If you read that book I mentioned it'll be your bible on gold.

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Bob,Handbook for Prospectors by Richard Pearl or older editions by VonBernewitz available online new or used at various prices or perhaps at your local public library.Maybe even free download from Google books.Also..How to find Gold by the late Aussie Ion Idreiss.These things should be read over and over..forever and when your out it in the field you'll apply what you've read after awhile.You can also read my sampling paper on goldplacer.com

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Right on, thanks Dave. I found out my library does have the Richard Pearl book, I'm just waiting for the last person to bring it back. The sampling paper is great, I have a printed copy that I keep in my car.

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