I'm currently reading The Mighty Dead, a book (not about mining) by Adam Nicholson which contains the following quote.

In some places, like the great copper body at Parys Mountain in Anglesey, copper was so thick in the groundwater that perfect branches, plant stems, leaves and nuts of the metal could be found in the dirt, where the mineral had somehow replaced the organic material buried there.

Is this likely? Whilst I'm sure that some limited form of replacement might be possible, the use of the word perfect seems a bit far fetched.

It is possible, there used to be a peat bog in the Dolgellau area that had a lot of 'perfect' replacement leaves, nuts, twigs etc

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This was Turf Copper Mine which overlies the Coed y Brenin porphyry copper deposit which contains 200mt of 0.3% Cu with trace Au. RTZ , its discoverer, was refused permission in the early 1970s to work it by means of an open pit mine, due to it being within the Snowdonia National Park.

http://www.mindat.org/loc-4285.html  provides the following summary of mineralisation in the vicinity of Turf Copper Mine:

"This location covers about a square mile of forest and rough country in the general area SH7425.

The pattern of the lodes is complex and over 30 adits and shafts are marked on the OS map. The most important lodes course northeast and southwest for about 900 yards and occur at surface in the Pen Rhos beds. Ore from these lodes carried chalcopyrite, pyrite and arsenopyrite in a quartz-calcite gangue. To the north another major lode striking in a more easterly direction carried gold in association with pyrite and chalcopyrite.

Perhaps the most interesting feature of the area is the "Turf Copper mine", where an accumulation of peat was found to contain high values of copper (some in the native state), with some being so rich that it was sent to Swansea for smelting in the condition that it was dug! Peat carrying less than two and a half percent copper was not considered worth extracting.

The total known output was around 1750 tons of copper ore from the "Turf Mine" between 1824-47, and 342 tons of gold ore giving 183 ounces of gold between 1854-65."

Could this be a form of petrification whereby a highly saturated solution deposits a layer of mineral on exposure to air? (as in petrifying wells?)

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Quite possible. At the Tynagh Mine in Galway, Ireland, the residual orebody of a black sulphidic mud contained perfect replacements in native silver-copper alloy of various organic objects including a remarkable silver newt in extraordinary detail.

In principle any material, which can supply electrons for the reduction process will be coated with a low reactivity metal.
In the cases described, silver and copper, more reactive metals, will undergo further changes.
This process has been used for years in copper mines to 'recover' copper from low grade ores and to make sure any effluent water has its copper ions removed.
In Anglesey it used to involve, scrap cars, but any scrap iron can be used.

In principle any material, which can supply electrons for the reduction process will be coated with a low reactivity metal.
In the cases described, silver and copper, more reactive metals, will undergo further changes.
This process has been used for years in copper mines to 'recover' copper from low grade ores and to make sure any effluent water has its copper ions removed.
In Anglesey it used to involve, scrap cars, but any scrap iron can be used.

IIRC my 'A' level chemistry, this only applies to 1 molecule thickness, hardly that as queried by the O.P.

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http://pubs.usgs.gov/bul/0795c/report.pdf  may be relevant as it considered the origin of metallic copper in a bog.

http://www.michigan.gov/documents/deq/GIMDL-GGNCD_302360_7.pdf 

Many years ago, I did an interpretation panel for the then Forest Enterprise at Turf Copper (part of the now-called Volcano Trail) where I used an interesting example via the British Museum of how metallic copper can replace, faithfully, organic matter. They have a specimen of ancient (Roman if I recall correctly) mine-timber from Cyprus, cut across the grain and polished. The copper replaces the wood in every detail - growth rings, the lot.

It is a pity that none of the copper replacements of leaves,
nuts etc were preserved when Turf was active. There are similar, smaller occurrences elsewhere in the vicinity - it would be an interesting exercise to trench one of them as the chance of finding similar material must be reasonable.

In principle any material, which can supply electrons for the reduction process will be coated with a low reactivity metal.
In the cases described, silver and copper, more reactive metals, will undergo further changes.
This process has been used for years in copper mines to 'recover' copper from low grade ores and to make sure any effluent water has its copper ions removed.
In Anglesey it used to involve, scrap cars, but any scrap iron can be used.

Yes it was "any old iron" that they had no practical use for. Simple example of double decomposition with the copper precipitating out and being scraped from the tanks as a finely-particulate sludge periodically. An early example of profitable recycling!

I think expelllo better go back to his text books!
Molecules are formed by the sharing of electrons and hence do not, generally conduct electricity.
We are looking here at a 'simple Redox reaction' some of whose principles I have briefly explained.

I think expelllo better go back to his text books!
Molecules are formed by the sharing of electrons and hence do not, generally conduct electricity.
We are looking here at a 'simple Redox reaction' some of whose principles I have briefly explained.

Didn't realise that electrical conductivity was an issue in this debate, BTW, impure water conducts electricity, but there again that is a compound solution:-[

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