OFD: Selenite tunnel: speleothems: colour: why?

Ralf

New member
Geology/mineralogy: Could someone please explain to me the colour of the speleothems in Selenite tunnel in OFD. Why the caramel/orange colour? Selenite? Gypsum? Sulphur? If so, why is there gypsum in a limestone cave?
 

AR

Well-known member
If you get iron pyrites present in veins/faults within the limestone then it'll tend to decompose in contact with water and form sulphuric acid as part of the process. That will then react with the limestone forming selenite, and take up some of the iron when it crystallises out giving it the colouration.
 

Fulk

Well-known member
I've a dim recollection of someone analysing orange stal. by dissolving it in acid and analysing the resulting solution. To their surprise they found no trace of iron, and eventually discovered that the orange colour was caused by the presence of the organic matter that stains peat run-off reddy-brown.
 

Pegasus

Administrator
Staff member
Ralf said:
Thanks! I feel educated now  :sneaky:

Me too - and from reading this thread:

https://ukcaving.com/board/index.php?topic=22791.msg287602;topicseen#new

;) :sneaky:
 
Top