While back in Cornwall recently, I was fouching around on Keneggy Beach looking for possible adits and came across a shaft on the western part of the beach, high up in the cliff face. I think it was a part of the Wheal Speedwell set.

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On clambering up to this shaft (it is well above the high tide mark) I was surprised to find that the air smelt strongly of rotten eggs. On peering down into the shaft I saw that it was flooded about 3 metres down and steadily bubbling what I assumed to be hydrogen sulphide gas.

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The only other place I have encountered this was at Harvey's Shaft on the Wallaroo Mines in South Australia ( I made 2 visits there - in 2004 and 2006 - so the phenomenon is continual). I wonder if anyone out there might have an explanation as to what might be causing hydrogen sulphide (if indeed that's what it is) to be escaping from the water like this? My first thought was that seaweed dumped in the shaft by extremely high tide might have been responsible for this, but as the shaft is very high in the cliff face and as there was no seaweed present inland at Wallaroo, I am stumped. A chemical reaction caused by bacteria partial to sulphide ore bodies perhaps? :confused:

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Probably either it is bacterial or chemical in origin. There is plenty of Iron Sulphide in old mines, so no problem there. I guess levels are low, otherwise it would stink for miles around. The nose is very sensitive to low levels of Hydrogen sulphide, so it is unlikely that any larges bubbles are pure H2S. Could be de-oygenated water + microbes feeding on sulphides in the mine.
Maybe worth trying to get a sample of the water and checking pH. Best bet to get it analysed maybe to get some local geologists interested at Tremough or Plymouth.
Other possibility is that someone has dumped something down there.

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This a very odd and will have to give it some thought. Hydrogen Sulphide escaping in sea water normally reacts with the dissoved CO2 and O in the water and in the case of hydrothermal vents forms organic matter but this obviously isn't the case here. Of course we are talking about far less pressure so may not be the case on or near the surface. The example in Australia seems to rule out sea water as a common factor anyway.

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The adit which is adjacent to the shaft has allsorts including a dead seal wedged in it. It was disgusting. Kenneggy has got a fantastic reef offshore which is kelp covered and rarely gets disturbed. When it does a fair bit of the kelp gets washed up and the sorts of conditions are the sorts to ram it back into that shaft.

I'd say there was some kelp in there which has been there a while, long enough for the water to go stagnant and anaerobic bacteria to get busy making their filthy farts. My money is on methane from these bacteria. Not sure where the H2S comes from but again, money on organic species.

There could be some very complex reactions taking place.....

Which one was the interesting adit?

The one at the back of the cleft with all the crap rammed in it, or the one with the partially blocked (on purpose?).

Anyway, you missed the really good one :lol:

I think your disguisting rotting seal has decomposed completely as Martin certainly didn't see or smell it in this adit:

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I take it that the above is the adit you mean which is not all that far from the bubbling shaft? Martin said it was choked with shingle near the entrance and the water was backed up beyond, probably over waist deep.

We have a friend at the British Geological Survey who can analyse water samples for us - he collects specimens from mines all over the UK. Would be interesting to know what is lurking in the water!

Hey Stuey, thanks for reminding me that we were thwarted by high tide from getting into 'that' adit :curse: !!!!! We'll be back...

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You're right, the seal adit isn't that one, it's the one at Wheal Prosper.

I'm no clearer as to which adit is Speedwell Mine out of those 2. The choked one has water flowing and so I assume that's it.

When I reckied Wheal Prosper Adit a couple of years ago (piccies on this site), it was absolutely jammed solid with plastic debris, bouys and large stones rammed in there by high tide. It would take some digging out :thumbdown:

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