Purple Stalactites

EFRESHW

New member
The image below was taken this year in a tourist cave. I saw this purple tinge on the bottom right on the calcite. There was no purple lighting I this photo. My question is; why on earth is it purple ? What mineral creates this purple tinge ? this is not the first time I've seen it happen. Lengthy scientific explanations welcome. Many thanks !


IMG-20220503-WA0058.jpg
 

Brains

Active member
Suspect if mineral in origin might be cobaltian calcite, as seen in the Great Orme, Alderley Edge and Clive Mine to name but three localities
 

EFRESHW

New member
thanks guys! been wondering this. I've seen it in showcaves just as much in non-show caves, so was wondering what it could be. Interesting about the lantern flora, because I've seen this in non-tourist caves, too! Maybe it's a mix of both
 

Ian Adams

Active member
I found this in a Welsh mine. I didn't know what caused the colouration so I asked around. I have forgotten (sadly) who finally answered the question but it was someone of repute - at Aberystwyth or Bangor university.

It was most likely the result of a cobalt deposit (also suggested) above. Possibly, so is yours.

Or, it might just be vimto.

Ian


form temp.JPG
 

Rob

Well-known member
If this is a show cave and they are actually purple due to mineral i'm sure they would be advertising to the moon about the purple stal!

Therefore much more likely it's either a trick of the light/camera or some flora/bacteria.
 

rm128

Member
I thought manganese deposits were mainly black in colour? Of course if there are other variants that would be good to know.
I’m certainly no expert on mineral deposits, but isn’t manganese purple in the +7 oxidation state (permanganate)? Whether that oxidation state is likely to occur in a cave environment is another question.
 

Brains

Active member
I’m certainly no expert on mineral deposits, but isn’t manganese purple in the +7 oxidation state (permanganate)? Whether that oxidation state is likely to occur in a cave environment is another question.
That is true but as mentioned Mn deposits are usually black in caves, being formed of the mineral pyrolusite.
 
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