Potch

[Wombats1]

I am basically a gold prospector, in my travels I have come across a place that has coke can sized iron protrusions (above ground) with a glassy opaque centre. It sounds like glass breaking and tinkling as it rolled around.

It is a huge dome shaped mound with these "coke cans" everywhere.

Looks a lot like potch but hey I have gold fever so it was only later I made the connection.

Is it possibke for large deposits of opal to form in what looks a lot like an extinct black smoker from an ancient ocean???

No photos (as not gold) I am a bit focused when out and about, but if it is possible I will head back out there and check it out is this a possiblity?

Google was not a lot of help,

 

[Dihusky]

If your working gold areas, maybe it's slag from gold pours?

 

[user 4386]

Without a photo you cannot really get a useful reply (a job for next visit). Without a general lovation it is even more impossible (e.g. why do you think you could be looking at a black smoker - even if you were it would not be highly likely).

Camera...action!

 

[Mike678]

Opal and gold are not in the same areas . Opal is found in sedimentary rocks like sandstone . Gold is in harder older rocks like quartz . Were a bouts did you see the "potch" ? Could be slag from a furnace ? After smelting the flux can be very glassy . Lot of slag produced when smelting copper .

 

[Wombats1]

Aahhh well that is the crux of the matter the area is also strewn with stromatalites thousands of them fill the creek (long dead)

I have been prospecting for gold since I was 15 old years now 56 also been employed in goldrooms and poured my share of 25 kg bars.

Not slag, just how you get ironstone surrounding opaque grey slag protruding from the ground I am unsure.

Really? No gold in sedimentary areas this deposit of gold sits right smack in the middle of a contact zone surrounded by sedimentary deposits ironstone is predominant but plenty of sandstone around. Then there are conglomerate layers as well

Queensland boulder opal is sedimentary ironstone? Or is it a misnomer and it is sandstone?

This area is pretty unique, the stromatalites place the location as a shallow sea eons ago, though perhaps their presence places the area in the wrong period? (Too old?)

I asked as I have not seen this in my travels before and it stood out as unusual, a friend recently dropped a peice of worthless potch into my hand he had collected years ago.

I recognised it as the same material, no doubt, but the location does give me pause as there are no major opal fields in WA that I am aware of.

Was hoping for more info as the location is very difficult to access, guess where I will be in 3 weeks

Cheers for the answers

 

[user 4386]

Stromatolites suggest you might be in a limestone area, so you might be looking at black chert.

The general comment about gold and opal not occurring in the same area is a valid observation

No significant precious opal in WA (tiny veinlets around Coolgardie - I have some - but it formed in a different way to our major opalfieds).

The ironstone that Queensland boulder opal formed in, formed differently to most ironstones (nodular ironstone concretions confined to the weathering zone).

Both gold and opal can form in sedimentary rocks, but not exactly the same type and not in the same area (most Victorian gold mines are in sedimentary rocks - without opal). There is a good reason why.

A photo should solve it.

 

[Wombats1]

The location was formed through oxidisation created by the oxygenation of a shallow sea by stromatalites, the predominantly ironstone ranges are believed to have been formed by this proccess, an accretion proccess?

Absolutely it could be something else, I will chuck up some photos when I get them. The whole area is just strange along with an overflow aquifer that flows down the creek and dissapears back underground. The gold deposits are couple of Kms away and spread through the area, this is in tesserated canyons looks like bricks, and is sandstone. There could be limestone around.

If it was potch that is all that is likely there, but a butchers hook will tell the story.

Reading anything I can find and yes it seems highly unlikely.

I have found that gold is where you find it, opal is probably similar