Little to no magnetite ?


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working a new claim in an area that has very very little magnetite.

This seems very strange to me yes theres gold placer yes there are gold mines in the area we found an old digging huge hole in the ground and coyote holes all over and quartz tailing piles all over, yes metal detected no gold just pyrite in quartz alot of rose quartz too

In the creek shallow bedrock its been creviced to death gold is in the creek in the bank areas and in cracks and under shallow hard pack, but why no black sands ?

Thanks guys learning about a new area sampling is a pain.

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Some areas just dont have it. Also, some of the very rich ancient river placers here in the motherload have no black sand also. All quartz. Sure makes for easier panning. I always thought it strange the big live rivers of today are loaded with the stuff but some of these ancient rivers had little to none. Makes you wonder.

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This is near Groveland and there's territiary around there we actually found volcanic rock in one area coming down a gully, stuff was broken down and had eroded down the hill so its up top that mountain some where, thanks Wes for the info

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Hi,

It just depends on what the general bedrock is made up of. A huge chunk of Alaska south and east of Anchorage has a slate, shale, and greywacke bedock that host gold bearing veins. There is very little magnetite in those sedimentary rocks and so you can run a suction dredge all day long and only end up with a couple spoonfuls of magnetite. Hot rocks are also nearly non-existant in the region.

Steve Herschbach

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I still find it weird how you can have a live river that is loaded with black sand and just up the ridge maybe a mile away a tertiary river, with the same general bedrock, and no black sands in it.

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Hi Wes, I pondered this same question for years. Were did the black sand go in those ancient placers?. and why do they look so bleached? and if there is black sand around or even above these placers now why not in them? This is the theory that made the most sense to me. In early history of the earth there were many ice ages that created huge ice caps even glaciers that covered much of the U.S.. and when the weather began to warm in between these ice ages the ice began to melt these huge ice caps some extending all the way to Mexico, created huge lakes some the size of the great lakes or even larger by some accounts. High water marks have been discovered on several mountain ranges in north western states. it is believed that catastrophic events such as earth quakes caused breaches in some of these lakes sending huge torrents of water sometimes billions of gallons of water across the landscape grinding small mountains away gathering gold and in some places carrying huge rounded boulders for hundreds of miles creating these ancient rivers channels and placers, and yes in many areas they also contained black sand or iron oxides and hematite and magnetite. were did they go? some geologist believe that volcanic activity in the area of these placers produced huge plumes of clouds containing sulfur dioxides and other gases then mixed with rain and created acid rain.... Yep acid rain was around long before automobiles, anyway these rains peculated down through the soil and eventually into these ancient placers were it basically leached the iron right out, dissolving it and carrying it down stream or into the ocean. this would also explain the etched surface found on the remaining cobbles in these placers, many are silica or silica based stones such as quartz, chert etc. that are highly resistant to acid. this also explains why the nuggets in some of these placers have such a bright color as the lessor metals such as copper, silver etc. were also leached from the surfaces of the nuggets in some cases creating an almost pure gold surface. Im going to take this a step further in time while Im here on this subject. How are the gravels then cemented? Over time, thousands or even millions of years and with the gravel no longer having enough water to move them the acid rains subside from less volcanic activity in the area allowing the water peculating down through these placers to switch from an acidic state to a more alkaline side of the PH scale and when this happens in areas were calcium and lime deposits are available. these minerals percolate down into the placers and into the cavities created by the removal of the irons and replace them filling the cavities and cementing them in place. Take care all, AzNuggetBob

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Hi Wes, Most of this theory is based on some reports I read years ago by several well known geologists and some by my own experiences.The story is a very condensed version of one I wrote several years ago. If I find the original papers written by the geologists on the net Ill post links. I found them very interesting and changed the way I looked at ancient placers completely.. If your interested in looking for them yourself I can give you some search clues that I remember about the reports but I don't want to drift to far off Vini's thread. I too have always been intrigued by ancient placers.

Hi Ron I appreciate your opinion on this, I have written many papers on mining over the years from geology theories to mining equipment but never published them. I have piles of them in the closet. I may reconsider putting together a book. Thanks AzNuggetBob

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Vini,

That old saying "Gold is where you find it". There's signs of different things to look for to indicate a gold bearing area. I've ran across a few places that you'd never expect gold to be found that have produce some fantastic day's with a sluice or dredge. The lack of blacksands reminds me of some old spots with a lot of granite in the higher country up above Mariposa, CA...you can dredge all day and clean up is easy!

Have a great Summer Vini.

LuckyLundy

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We're lookin up there too Lucky

There area were in is Tertiary it actually falls into another era that the Tertiary falls into and 2 others I believe at least from what I have gathered so its good ground just have to keep diggin in , thanks guys

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