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Re: Salt lakes and nuggets
September 02, 1999 at 18:39:41
In Reply to: Re: Salt lakes and nuggets
posted by Chris ( Kalgoorlie ) on September 02, 1999 at 17:34:47
Chris, Thinking of going overseas ???
I have often though about lake gold and it's formation in or around the lake. Does it precipitate and "grow" in the lake? Sometimes a lake nugget will be a solid worn peice,obviously travelled. Therefore it didn't grow in the lake.
Other times it will be so sharp that you can cut your finger on it - hardly moved at all- with holes in it and with a very jagged contour. It really is beautiful stuff when it is comes up like this. My theory here is that the nugget was washed into the lake bed as a specimen and the mildly corrosive environment of the "alkali" clay has eaten away the host rock and all that remains is the gold - looking as if it has just come out of a bowl of HF acid!!
There is still a LOT of gold in W.A. salt lakes,but the lakes are so big you could spend a lifetime skidding across 'em and still not cover them all.
The precipitation "growth" theory is realistic,though. I have been informed that around Kalgoorlie,at the base of those huge tailings dumps left over from the turn of the century,that small nuggets have been found. These have precipitated from the tailings dirt left by the old mining companies. This dirt can go 10 grammes to the ton,but was irrecoverable by older methods of extraction. The rainfall of 100 years has precipitated that "10 grammes to the ton" into tiny,barely visible nuggets.
As for Lake Lefroy,I have had gold up 500 meters from the edge,but none actually in it. From the area that I visited some years ago I would say that the alluvium leading into Lake Lefroy is so wide on the lake fringes that the gold is there,trapped under the sand and it's just too deep. Other lakes seem to have a more rapid transition from the gold bearing rocks to the lake bed. On Lefroy there is kilometers of sand to get over before you hit the lake bed. Maybe that's the reason.
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