Matlock: cinnabar

[gus horsley]

I'm interested in mineral formation and I've read several reports mentioning cinnabar in some of the mines and caves in the Matlock area, particularly Rutland Cavern.  Can anyone shed any light on how it was deposited?

 

[danthecavingman]

https://www2.imperial.ac.uk/earthscienceandengineering/rocklibrary/viewminrecord.php?mID=141

Cinnabar forms in low temperature Hydrothermal veins - just the same as the other main ores in the Derbyshire field. I guess Cinnabar occurs less frequently because Mercury is a much rarer metal than Lead for example.

Dan.

 

[AR]

I don't think it occurs in significant amounts anywhere in the Peak, I once saw what I thought was a tiny crystal of the stuff inside a calcite vugh in the Blende vein, Magpie Sough but I wouldn't swear to it having been cinnabar. I presume you've already looked at this? http://www.pdmhs.com/PDFs/ScannedBulletinArticles/Bulletin%2012-1%20-%20The%20Minerals%20of%20the%20Peak%20District%20of%20Derbyshire.pdf

 

[gus horsley]

Thanks for the replies.  I'm going to have to look further into this as I think the cinnabar may be linked to decomposition of galena or possible sphalerite. I might be guessing but, although in some locations it would be of primary hydrothermal origin, I suspect that's not the case in Derbyshire.  I'll post whatever I come up with.

 

[AR]

I'd be more inclined to think it was part of the primary deposit, since most of the other metal sulphides are, and there can be significant variations. Ignoring the Ecton deposit which has been suggested as having a different source, copper is generally absent or only present in miniscule amounts in the Peak District veins, but it appears in significant patches in odd places, so why not other metals?

 

[gus horsley]

I've just been looking at Minerals of Britain and Ireland by Andrew Tindle and he says that the Rutland Cavern cinnabar is found in small vughs in fluorite associated with smithsonite (formerly calamine) and consists of tiny brick-red flakes.  There's no mention of genesis so I'm still guessing as to whether it's primary or a secondary breakdown of sphalerite/galena with native mercury along cleavage planes.