Yesterday, due to the overnight weather on Saturday, I visited Seathwaite Wad Mines in Borrowdale in the Lake District. In a chamber just off the main passage of the Giles or Gills Stage there are some straws and the beginnings of some curtain formations. These formations are limited to a small corner of the chamber and there are some lesser formations in a small side passage.
Nothing strange there you may think, except that the fell, part of the Great Gable massive, is granite from valley floor to summit. To be accurate the granite is of the Borrowdale Volcanic Series and is the result of 4 million years of near continuous vulcanism.
Given that I cant see how there could be any limestone in the vicinity, what are the formations made from. Another question would be what other water soluble minerals can cause 'Stall' formation, ideally minerals that would be present in igneous rocks?

has anyone dumped a load of Lime on the hill above?

Can't see why anyone would. The fell above the mine is about a thousand feet above valley level, inaccessible except on foot and the abode of sheep.

Granite and volcanics are NOT the same thing at all, and there are many Ca bearing minerals within both... In addtion late stage mineralisation containing Calcite is not uncommon. While it may be rather unusual, it is not really that puzzling, particularly given the localised nature of the formations... You do not say what colour the things are - asuuming approaching "white" then calcite or maybe gypsum are the most likely, other similar appearing things of differing colour could be iron or manganese formations...
lastly, if the things were reasonabley distant from the entrance / draughts, they maybe snotites - not as rare as once thought - but they would have to be soft in this case, unless subsequently petrified of course.

or was concrete used in any of the mines construction?

.

martinr said:

mak said:

or was concrete used in any of the mines construction?

Click to expand...

I think the graphite mines are Elizabethan? Doubt they used concrete then.

Click to expand...

The graphite mines have iron plate rails in them. Definitely 19th century in part.

Brains said:

Granite and volcanics are NOT the same thing at all, and there are many Ca bearing minerals within both... In addition late stage mineralisation containing Calcite is not uncommon. While it may be rather unusual, it is not really that puzzling, particularly given the localised nature of the formations... You do not say what colour the things are - assuming approaching "white" then calcite or maybe gypsum are the most likely, other similar appearing things of differing colour could be iron or manganese formations...
lastly, if the things were reasonabley distant from the entrance / draughts, they maybe snotites - not as rare as once thought - but they would have to be soft in this case, unless subsequently petrified of course.

Click to expand...

That sounds feasible.
You obviously have a far superior geological knowledge to myself, not that that would be difficult.
Lakeland Rocky Rambles and the FRCC guide to Borrowdale both state the rocks in that part of the valley are volcanic in origin. I also seem to remember a book called The Volcanoes of Borrowdale. I'll Google it.

Glossary of the minerals of the Lake District (BGS):

CALCITE
CaCO3 Trigonal

A very common mineral throughout many parts of the area occurring in a wide variety of environments and parageneses. It is, of course, the main constituent of all the limestones and is also commonly present in small quantity in many other sedimentary rocks either as included grains or as a cement. Many of the igneous rocks of the area contain small amounts of calcite, mainly as a secondary mineral and in places filling vesicles. Calcite is an important gangue mineral in the hematite ore bodies of west and south Cumbria and Furness: very fine crystallised specimens have long been famous from these deposits. It also occurs as a gangue mineral in several of the metalliferous veins of the central Lake District though in general, it is not common here and is only found in quantity at a few localities.

The following list is, of necessity selective. Included are those localities which have provided good specimens or in which the mineral shows other features of interest. A representative selection of other modes of occurrence is included.

[long list of localities follows...........]

Graphite Mine, Seathwaite, Borrowdale [NY 232 125J:With galena, quartz and chlorite (Strens, I 965)~
In altered diahase (Mitchell & meson, 1973).

Thanks for the replies. I didn't realise calcite was so common in igneous rocks.  Thinking about things more closely, most of the running water in the mine has run in from the surface via various tunnels and shafts. Where the formations are the water appears to be seeping through fissures in the rocks, cave style so to speak. Looks like good old calcite is the cause.
Again thanks.

In a similar vein- can anyone shed any light on what causes different formation shapes. having recently found straws and curtains in close proximity to each other in a terminal chamber without any strong drafts. why would they not all form in the same shape?  :-\

Curtains are formed by a trickle of water flowing downhill across the roof. As the water flows, calcite is deposited.
Straws are where the water has found a local low point on the roof and would need to go uphill to get anywhere from there (which is clearly impossible in normal circumstances) so it collects there until it forms a drip too large for the surface tension to support it against gravity. As it falls it deposits a small amount of calcite that forms the straw.

Straws form at the diameter of a drip of water and the drip's diameter is defined by gravity and the forces within the water (surface tension). On earth a water drip is approximatly 6mm across which is why straws form at that diameter. On a smaller planet they would have a greater diameter.

It is possible (and quite common) for a curtain to end with a straw, as the flow finds a localised low point and cannot travel across the roof any further, it forms into a drip at the end of the curtain.