Purple Stalactites

[EFRESHW]

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 !

 

[ChrisJC]

Maybe a bit of erythrite has got into the water.

Erythrite - Wikipedia

en.wikipedia.org

Chris.

 

[cap n chris]

Lampenflora can cause this and the nearby green rather suggests that is what's going on.

 

[Brains]

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

 

[Pitlamp]

Lampenflora can cause this and the nearby green rather suggests that is what's going on.

Reckon Chris could be right. Specifically, cyanobacteria can be that sort of colour.

 

[EFRESHW]

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]

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

 

[The Old Ruminator]

There is one in Shatter Cave.

 

[rm128]

Manganese?

 

[Alex]

I had a similar question and it was suggested it was some kind of bacteria amongst other things...

UKCaving: Purple passage

 

[mikem]

Some ochre is also purple (due to other minerals mixing with the iron)

 

[ZombieCake]

Manganese?

I thought manganese deposits were mainly black in colour? Of course if there are other variants that would be good to know.

 

[Rob]

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]

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]

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.

 

[wormster]

Have you tried shining a uv lamp at it?? The formations might glow, some minerals do!!