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Mine Exploration Forum

Author Grove Rake PDHMS meet 1989 (probably) (photo)
John Lawson

Joined: 09/12/2010
Location: Castle Douglas Dumfries & Galloway

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Grove Rake PDHMS meet 1989 (probably) (photo)
Posted: 13/11/2018 20:42:14
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Hi This is almost certainly the famous marcasite vugh!
To those of you who are not aware, Marcasite is similar in Chemical formulae to the more we’ll known Iron Pyrites.
The main difference being marcasite is not very stable and in damp air will rot to nothing!
Hence the interest at the time and the collecting foray!
Under certain circumstances Marcasite can even be pyrophoric, ie it will burn when it meets the air. Tara Mine in Ireland had some problems with this mineral, of this nature. As far as I am aware this catching fire never happened at Grove Rake....replace this line with your message...

Photograph:



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IP: 86.179.100.12
Jim MacPherson

Joined: 02/09/2015

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Grove Rake PDHMS meet 1989 (probably) (photo)
Posted: 14/11/2018 10:16:13
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Hi John,

Thanks for that nugget, I'll add the info to the pic.

I'll need to have a delve through the bits of Dad's mineral collection I kept (quite a lot went to Kilhope) and see if there is a piece lurking and it's also interesting to note that there is more than one way of spelling vug, which is even better in ScrabbleSmile

Jim
IP: 86.149.33.77
Peter Burgess

Joined: 01/07/2008
Location: Merstham. Or is it Godstone ...... ?

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Grove Rake PDHMS meet 1989 (probably) (photo)
Posted: 14/11/2018 14:02:26
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That's fascinating. I only learnt this year that the so-called marcasite nodules found in the chalk may well be pyrite after all. I don't know how true this is. IP: 85.115.54.201
Minegeo

Avatar of Minegeo

Joined: 17/06/2008
Location: Ireland

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Grove Rake PDHMS meet 1989 (probably) (photo)
Posted: 14/11/2018 22:13:17
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Actually the marcasite at Tara was generally crystalline in crosscutting veins within the lower ore lenses and was not an issue for mining. The issue was in the Conglomerate Group Ore ("CGO") which contained massive but very fine grained framboidal metastable non-stoichiometric marcasite. Occasionally this sulphide would cause a pre-ignition blast whereby when a round was fired the cut would produce a dust cloud which would then ignite and cause the entire round to pre-ignite. The resultant explosion known as a sulphur-blast would cause extensive damage to mine infrastructure such as pipework and vent bags.


Similar problems were encountered in the Upper G Zone and B Zone at Silvermines where very brassy metallic pyrite caused the occasional sulphur blast.


The problem could be prevented by inserting lime capsules in the blast holes.



IP: 207.189.0.3
Boy Engineer

Joined: 20/06/2008
Location: Derby

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Grove Rake PDHMS meet 1989 (probably) (photo)
Posted: 15/11/2018 17:08:59
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fine grained framboidal metastable non-stoichiometric marcasite

That's easy for you to say. Laugh
IP: 83.216.139.158
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