What is Moonmilk?

[Peter Burgess]

In this article, we provide a review of geomicrobiological interactions in caves, which are nutrient-limited environments containing a variety of redox interfaces. Interactions of cave microorganisms and mineral environments lead to the dissolution of, or precipitation on, host rock and speleothems (secondary mineral formations). Metabolic processes of sulfur-, iron-, and manganese-oxidizing bacteria can generate considerable acidity, dissolving cave walls and formations. Examples of possible microbially influenced corrosion include corrosion residues (e.g., Lechuguilla and Spider caves, New Mexico, USA), moonmilk from a number of caves (e.g., Spider Cave, New Mexico, and caves in the Italian Alps), and sulfuric acid speleogenesis and cave enlargement (e.g., Movile Cave, Romania, and Cueva de Villa Luz, Mexico). Precipitation processes in caves, as in surface environments, occur through active or passive processes. In caves, microbially induced mineralization is documented in the formation of carbonates, moonmilk, silicates, clays, iron and manganese oxides, sulfur, and saltpeter at scales ranging from the microscopic to landscape biokarst. Suggestions for future research are given to encourage a move from descriptive, qualitative studies to more experimental studies.

I like the idea that it is salt from the castle sh1te pit.

 

[gus horsley]

There's a weird bacterial deposit in Cae Coch Mine (Conwy Valley) that was tentatively called snotalite because that's what it resembles: cold snot.  Only there's tons of the stuff growing down a waterfall.  It apparently extracts carbon dioxide from the atmosphere and combines it with sulphuric acid in the water to produce a sugar which it eats.  Or something like that.  The water in the mine will burn your feet if you get a wellyfull and we once measured the pH of a drip from a stal at 2.5 which is stronger than battery acid.  It's amazing what will survive in an apparently hostile environment.

 

[ian mckenzie]

http://en.wikipedia.org/wiki/Snottite

 

[tubby two]

I thought moonmilk was more the wite gloopy stuff on mine walls or old woodwork, some kind of bacterial deposit- although this sounds more like the 'snottie' described above. I'll have to test the ph when i next go down a mine with some in.

tt.

 

[Brains]

Snottites are a bacterial goo that looks and feels just like snot. It lives by converting sulphide to sulphate, using that energy change instead of the conversion of oxygen. It can live entirely without O2, but does rerquire high levels of sulphide, most commonly Iron sulphide - Pyrite. It will only be found where this is present, so old metal mines. It is also quite rare. In appearence it is quite translucent, coating the walls, or hanging down as long dripping snots, which will wobble and swing in a breeze... truly bizarre, but unrelated to moonmilk

 

[Glenn]

The water in the mine will burn your feet if you get a wellyfull and we once measured the pH of a drip from a stal at 2.5 which is stronger than battery acid. 

If I remember the circumstances correctly, I had just waded through the knee deep water, when Gus turns around and says, a little too late, "whatever you do, don't get water in your wellies, 'cos it's stronger than battery acid!" A good trip though, and it cured my athletes foot.

 

[MSD]

As far as I am aware, moonmilk grows in the dark and forms in conjunction with mainly bacteria, whereas tufa grows outside and is mainly precipitated by algae.

Mark

 

[ian mckenzie]

http://en.wikipedia.org/wiki/Moonmilk  Not much here but the links are interesting.

 

[graham]

To get back to the original question, the most common mineral deposits in caves and tunnels are calcite and gypsum. The "rule of thumb" (i.e. it works a lot of the time but isn't gospel) way of telling them apart is that calcite formations grow at this end - on the tip of a stal or a straw, on the outside edge of curtains etc. - whereas gypsum crystals grow at that end - so gypsum needles or flowers appear to have been "extruded" from the rock surface.

graphically (if this works) 1, 2, 3, is a time sequence:








calcite:                                                          gypsum:


          ------------------ rock surface                          ------------------ rock surface
                      1                                                                    3
                      2                                                                    2
                      3                                                                    1


Hope that makes sense.

 

[Peter Burgess]

If I get a small sample of the white substance, is anyone here interested in analysing it for me? For nothing, of course - I am a caver, remember!

 

[graham]

Nope, I gave away my bumper fun chemistry set many years ago.

 

[Peter Burgess]

Wrong answer, Graham. Anyone else?

 

[Limestone_Cowboy]

I work as experimental officer in charge of a scanning electron microscope and if a small sample was sent to me I could have a go at identifying it for you. I can take pictures, do chemical analysis and perhaps even do a bit of crystallography on it depending on the sample.
PM me if your interested and I'll send you my address.

Nick

 

[Peter Burgess]

Ooooh that's very kind. A suspicious plastic envelope containing an unknown white powder will be on its way to you at some time. A report with appropriate credits might result. Or I might get arrested.

 

[Peter Burgess]

To get back to the original question, the most common mineral deposits in caves and tunnels are calcite and gypsum. The "rule of thumb" (i.e. it works a lot of the time but isn't gospel) way of telling them apart is that calcite formations grow at this end - on the tip of a stal or a straw, on the outside edge of curtains etc. - whereas gypsum crystals grow at that end - so gypsum needles or flowers appear to have been "extruded" from the rock surface.

graphically (if this works) 1, 2, 3, is a time sequence:








calcite:                                                           gypsum:


           ------------------ rock surface                           ------------------ rock surface
                      1                                                                     3
                      2                                                                     2
                      3                                                                     1


Hope that makes sense.

Thanks Graham. I never really appreciated this. You must have spent ages typing that in!

 

[gus horsley]

Gypsum needles also appear to be extruded because they sometimes appear to be curved.  In Cae Coch, which I mentioned earlier, there are some melanterite crystals (copper and iron sulphate) which are/were several inches long, blue-green and curved.  They had extruded out of muddy deads.

 

[Peter Burgess]

Yours truly collecting a sample yesterday for analysis.

 

[cap n chris]

"Collecting for analysis", my arse!

You were using a goddam trowel to shovel up WAY more than your fair share of marching powder at an overly generous New Year's Party, you lucky sod. 

 

[Stupot]

Where's your life line and helmet  :spank:

 

[Dep]

"Collecting for analysis", my arse!

You were using a goddam trowel to shovel up WAY more than your fair share of marching powder at an overly generous New Year's Party, you lucky sod. 

Very good.