This chat comes up from time to time and there are seemingly several different points of view over what it actually is.

I assumed the dark colours were attributed to Cu Sulphates and the more green varieties from Carbonates. A geologist informed me that it was Chrysocolla, a Cu Silicate. I'm unsure if there are so many varieties of colour, how they are attributable to one mineral species? Hmmm.

A while ago, I attempted to reduce what I thought to be largely CuCO3 to copper metal in my back yard. I got a very poor yield and a large amount of "clayey" stuff. I assumed this to be residual silicate.

I've seen a fair old amount of coloured "toothpaste" from white to varieties of yellow and orange.... obviously stained by different compounds. Whilst the underlying matrix is clearly silicate based, I think the colours are in the majority due to finely divided minerals being caught up in that structure. I would say designating "It's Chrysocolla" a bit short sighted.

Am I wrong?

Here's a case in picture

Stuey,

I would imagine the make up depends on the individual deposit, as you are no doubt aware there are lots of different ores of Copper, some common some rare, these include Silicate, Carbonates and Sulphides (I guess there is also Oxides of copper, but I doubt it would leach to easily). If the ore is principally A sulphide, the chances are the staining is copper sulphate, if its a silicate ore, it will be copper silicate, etc.

This is pure hypothesis on my part

I don't fully understand the process by which primary sulphide ores end up as carbonates and sulphates, but it's not direct. For instance, you need CO2 dissolved (from the rocks) in order to get carbonates, but the CO3 ion has to be more reactive than what it replaced, perhaps by the sulphide reacting with something more reactive..... jeez.

I suppose my question was whether the blue stuff is actually chrysocolla (with a fixed ratio of Cu:O:Si with added stuff contaminating it, or whether it was a Si-O chain with all sorts of oddities hanging off it.

In my estimation, the blue/green/white stuff we see is Silica (amorphous) with aggregations of other minerals MIXED with it, rather than bonded to it.

I'd like a definitive answer from an expert! :thumbsup:

I would like to reverse this discussion briefly if I may, what about no stain at all?
Over the years I have picked up, albeit small samples of native copper both at surface and underground, all have been as copper metal would appear with no staining at all despite being exposed to the elements.
I have discussed this with several geologists but have never had a straight answer

---

I would like to reverse this discussion briefly if I may, what about no stain at all?
Over the years I have picked up, albeit small samples of native copper both at surface and underground, all have been as copper metal would appear with no staining at all despite being exposed to the elements.
I have discussed this with several geologists but have never had a straight answer

A wild guess that the native copper is in a weak acid environment?

I would like to reverse this discussion briefly if I may, what about no stain at all?
Over the years I have picked up, albeit small samples of native copper both at surface and underground, all have been as copper metal would appear with no staining at all despite being exposed to the elements.
I have discussed this with several geologists but have never had a straight answer

Are we dealing with chunks of well formed metal or powdery coppery stuff?

You quite often find copper metal aggregates where iron has buggered off with the (usually sulphide) from copper.

For rails and iron stuff.

CuSO4 + Fe ----> Cu + FeS04 (Cu left behind as pinky powdery metal)

If you find stuff which has aggregated into more of a consolidated lump, it was probably done as a part of the mineralisation, ie:- various chemical pathways leading up to the precipitation of copper as a metal and something which was kicking around lonely (for some other chemical reason which runs into a squillion options) for it to nick whatever was attatched to the copper.

The simplest version is to consider CuSO4. Things like Malachite are not soluble and would not undergo reactions with "stuff" resulting in the metal being precipitated.

Quite a few precipitation works took advantage of this reaction in order to "turn" Fe into Cu!!!! Surprised the pikeys haven't dammed adits and filled them up with bits of old car.

I'd like to boil dry about 5L of mine water and see what I got.

If you had 3 metals in a bucket of distilled water and you slung in some sulphuric acid, the most reactive metal would form the sulphate first. Then once that was all sulphate, the next metal would do the same, etc. If you then took your bucket of 3 types of metal sulphate and slung in something which was between the reactivity or 2 and 3. The 3 would be precipitated and the new stuff would form the sulphate..... where you get copper, this has happened, either simply or by a hugely complicated pathway...

I would like to reverse this discussion briefly if I may, what about no stain at all?
Over the years I have picked up, albeit small samples of native copper both at surface and underground, all have been as copper metal would appear with no staining at all despite being exposed to the elements.
I have discussed this with several geologists but have never had a straight answer

A wild guess that the native copper is in a weak acid environment?

In some cases yes in others no. Where I can guarantee that it will be found quite easily is at the Long Grass slate quarry near Tintagel. these bits range from the size of a thumb nail to a little larger than a postage stamp and are about 1/64" thick all have a brilliant shine and lie upon the slate. The others I have found are at Consols' and are more like wire wool made of copper, the best piece I ever found was at Mount Wellington, I put it down to retrieve latter but couldn't find it so it's there waiting for someone else

---

I know that at Coniston the blue formations that Coniston is so famous for, are secondary copper mineralisations (sorry, obvious).

Acidic surface water working its way down through the ground and into untapped ore bodies dissolves the minerals and causes crystallisation of the colourful copper formations. The blue and sometimes green formations are called supergenes and consist mainly of copper sulphates, with a little of copper carbonates. This has been confirmed by a study performed by a chemist.

---

I have several fotos of the "waterfall" in Tankardstown mine, co Waterford eire, there are so many shades of blue it`s amazing, most of the material in that mine is copper sulphate, mostly non-crystalised, a wow factor of 10

---

Been told that the bluer bits are more azurite and the greener more malachite, both are complexd with water and other stuff there are very rarely any pure bits just mixes of difrant minerals and there are 100s if not 1000s of ones for cu cause its such a complex chenistry
also in a weathered vein you will get a seqrnce down of mineral from native through oxides cox sox and sulphides to unalteredd ore
dont get it myself but its what i have been told

---

They tend to be a complex mixture of basic hydrated copper sulphates - things like langite, brochantite, posnjakite etc in many areas. Mines near the coast have chlorides too due to seawater interaction - things like connellite and botallackite. Mines where the environment's a bit alkaline see more carbonates, while acidic mines like Parys Mountain have sulphates like chalcanthite. It varies a lot according to where the mine is situated, its host rocks and its lode mineralogy.

These secondary minerals are interesting in the sense that they act as reservoirs for copper and other heavy metals i.e. they are precipitating out rather than continuing their journey towards watercourses etc. In an extreme example of this, studies into the lead chlorophosphate mineral pyromorphite have shown that it is by far the most stable lead compound in nature - if you precipitate lead from solution as pyromorphite you pretty much render it inactive!

Cheers - John

Good Stuff

Cheers John. Interesting input...

You share my original ideas totally.

If no evaporation or competetive dissolving (if that's a term) is taking place I can't see why any precipitation would be taking place. I've also tried to dissolve>>>filter>>>recrystallise the stuff and found most of the stuff is virtually insoluble. As I mentioned, all copper salts (containing O)will decompose to the oxide with strong heating. This stuff is insoluble and so it's nigh on (under shed conditions) to separate the "clayey stuff" (Which is unreactve with strong acids-silica?).

I got this far and then attempted to reduce the oxide with coke and a serious furnace and got a yield of about 2% of what I expected. The remainder was a white powder and a few puny nuggets.

I wonder whether there is a combined truth which involves both silica and micro crystals of the relevant mineral adhering (chemically) to the silica gel.

Hmmmmm. I'm convinced that the label of chrysocolla is wrong as it's technically a mixture....?

Easy way to get an individual copper stain identified is to take a sample. I don't mean hack it all away - simply a few matchead-sized bits will do. Then get one of the leading Museums - National Museum of Wales, British Museum (Nat Hist) or Oxford University Museum to identify it using x-ray diffraction or infra-red spectroscopy - they all have the kit to varying degrees.

Incidentally, in many cases, the stuff is only stable in a damp underground environment and crumbles to dust at room temperature - especially the hydrated sulphates, so the specimen value is minimal.

Cheers - John

you are right John, the staining at Tankardstown turns to powder when dry, which is why I ask visitors not to take any,its pointless, plus spoils the colourful flow on the walls, I have done a lot of work in that part of the mine over the last 15 years, the only stable mineral is langite from the mine, also found cobolt stained calcite in one small spot, so I hid it !! ( covered it in situe). written a few papers on the mineralisation with Dr R.S.W.B.
Must e.mail you, not done so for a while.

---

I asked about this in November:

www.aditnow.co.uk/community/viewtopic.aspx?t=2125

and was given the link to an earlier discussion which covered the topic in considerable detail.

www.aditnow.co.uk/community/viewtopic.aspx?t=1159

Seems a mineral collector, who is also a chemist, has analysed them and published the results in a mineralogical journal. I have recently got a copy of the journal, although the article in question is highly technical, and rather above my head. For those interested the bibliographic reference is:

S. Moreton, (2007) "Copper-bearing silica gel from the walls of Tankardstown mine, Co. Waterford, Ireland." Journal of the Russell Society, vol. 10, p.10-17.

According to his results, the soft slimy stuff is not chrysocolla, but is silica gel with copper bound to it by "cation exchange with the protons on silanol groups" (please don't anyone ask me what a silanol group is). Although not chrysocolla, these coatings may, however, be a sort of precursor in its formation. Given enough time it seems they may polymerise and harden into proper chrysocolla. The paper is full of graphs and tables and references to the technical literature on the chemistry of copper and silica gel. He clearly knows his stuff, and the paper is the definitive work on the topic.

Cheers Chris, that tells me all I need to know!